This guide covers the 10 UK-based Klaviyo agencies we'd shortlist for a Shopify brand in 2026, what each one is built for, and how they compare on partner tier and location.
Written by
Oliver Kenyon
Co-Founder & CEO
This guide covers the 10 UK-based Klaviyo agencies we'd shortlist for a Shopify brand in 2026, what each one is built for, and how they compare on partner tier and location.
Most Shopify brands we work with share the same blind spot. A new landing page lifts conversion, more first orders come in, and those new customers land in a Klaviyo welcome flow nobody has touched since launch.
At ConversionWise, we've spent 13 years on what happens between the click and the checkout, across more than 4,000 Shopify brands. Good conversion rate optimisation wins the first order. Klaviyo is where the second, third and tenth orders come from, and that work needs its own specialist.
This guide covers the 10 UK-based Klaviyo agencies we'd shortlist for a Shopify brand in 2026, what each one is built for, and how they compare on partner tier and location.
The best Klaviyo agency for Shopify brands in the UK in 2026 is Underground Ecom, a London-based Klaviyo Elite Master partner named Klaviyo's Agency Partner of the Year EMEA 2025.
It runs retention and everything else across email, SMS and WhatsApp, with a team of 120+ retention marketers and benchmarks drawn from over 500 brands.
Soar With Us suits DTC brands that want paid social and retention under one roof, Email Kong suits brands that want a Klaviyo first CRM build, and Velstar suits Shopify brands that need the store and its integrations handled too.
Every agency here has a UK base, holds a current listing in Klaviyo's partner directory, and works with Shopify brands. We checked each partner tier in the directory in November 2026.
We also looked at how central Klaviyo is to each business, whether it names Shopify clients or results, and what size and type of brand it is built for.
Klaviyo tier: Elite Master.
Based in: Headquartered in 103 Farringdon Road, London EC1R 3BS.
Best for: Growth-stage Shopify and DTC brands that want retention treated as its own discipline.
Underground Ecom is the only agency on this list that does retention and nothing else.
There is no store build or paid media arm, so email, SMS and WhatsApp are planned as one programme rather than three competing calendars.
That focus earned it Klaviyo's Agency Partner of the Year EMEA 2025, announced at K:BOS in Boston.Its team of 120+ retention marketers works with more than 150 ecommerce brands worldwide.
Underground Ecom’s team are Klaviyo specialists first.
Flows, segmentation, predictive data and campaign builds all run inside Klaviyo, so Shopify order and browsing data drives every message rather than sitting unused.
That expertise extends to the subscription tools Shopify brands rely on, including Recharge and Loop.
Replenishment reminders, failed payment recovery and cancellation saves are built around the subscription platform’s own data, which matters for supplement, food and beauty brands where most profit comes from the third order onwards.
The wider stack is covered too, from Attentive for SMS and Smile.io for loyalty to Okendo and Yotpo for reviews.
For a Shopify brand, that means one team that understands how every app feeds Klaviyo, instead of several vendors working in isolation.
The first reason is Underground Insights, a proprietary benchmarking tool that is free for active clients.
It measures each account against a dataset of over 500 brands, with vertical-specific benchmarks and lifecycle revenue mapping that native Klaviyo dashboards don't show, and it flags the team within the week if flow revenue dips below its historical baseline.
The second is the team model. Each brand gets a CRM Director as operational owner, a CRM Manager on day-to-day execution, dedicated designers and copywriters, and a senior strategy layer, instead of a single account manager.
The third is range.
Clients include AG1, Huda Beauty, Wild, Spacegoods, Oh Polly and Chilly's, yet the client base runs from early-stage challengers to global, multi-market businesses. For a Shopify brand that is still scaling, that means enterprise-level process without needing an enterprise-sized list.
SeoulBox sells subscription boxes of Korean snacks and K-pop merchandise, with email as the centre of its marketing.
Underground Ecom rebuilt its strategy around a pop-up list growth plan, rigorous testing and personalisation.
In the SeoulBox case study, email revenue grew 287% within six months, email came to drive 41% of total revenue, and revenue per email recipient doubled.
Most brands start with a free CRM Impact Session. It benchmarks the account against competitors in the same DTC vertical, maps where revenue is lost across the customer lifecycle, and ends with a concise impact report and prioritised next steps.
From what we were able to find about them, Underground Ecom’s engagements start from £3,000/month (about $4,000/month).
Klaviyo tier: Platinum Master.
Based in: Leeds.
Soar With Us describes itself as a full-stack ecommerce growth agency, focused on paid acquisition and retention for DTC native brands. Founded in 2019, it now has around 120 staff and took a majority stake in creative studio Hambi Media.
It works with about 65 brands, including Mindful Chef and Cowshed, and reports more than £200m in revenue delivered for clients. That suits Shopify brands scaling on Meta and TikTok that want Klaviyo planned around the same customers.
Klaviyo tier: Platinum Master.
Based in: London.
Email Kong calls itself a Klaviyo first CRM agency for DTC brands. It builds complete CRM systems inside Klaviyo, with lifecycle strategies that connect acquisition, retention and customer service across email, SMS and WhatsApp.
Its directory listing covers Shopify, Shopify Plus and WooCommerce. Pricing is quoted per scope, and heritage workwear retailer MC Overalls is among its named clients.
Klaviyo tier: Platinum Master.
Based in: London, with a team in Sofia.
Thrivelia reports more than $150M in tracked client revenue across 130+ consumer brands. Its eight stage framework treats the first purchase as the middle of the customer journey, and every engagement starts with a diagnostic audit.
It reports results on last click, seven day attribution, which gives founders a clear and conservative read. Clients include KEF, Printfresh and Pulsetto.
Klaviyo tier: Platinum Master.
Based in: Leeds.
FUTCOM is a social first agency with almost ten years of work for UK brands, and it holds top-tier partnerships with Meta and Pinterest as well as Klaviyo. It pairs business consultancy with agency delivery, working as an extension of the client's own team.
Clients include Moda in Pelle, Daniel Footwear, Graham & Green and Happy Beds.
Klaviyo tier: Platinum Master.
Based in: Bristol.
Flourish started in direct mail and is now a specialist CRM agency working across platforms, channels and data. Its Klaviyo work spans email, SMS, RCS, WhatsApp and push, and it won a DMA Gold award for Best Use of Email in 2025.
Clients include Nissan, Pai Skincare and Wonderbly, so it fits Shopify brands whose CRM already reaches well beyond email.
Klaviyo tier: Gold Master.
Based in: London.
Unified is an ecommerce agency covering strategy, development and design, data and analytics, and growth. Its Klaviyo work includes Klaviyo Data Platform implementation, useful for brands joining up store, customer and marketing data.
Clients include Tom Dixon, The Conran Shop, Boodles and iCandy.
Klaviyo tier: Gold Master.
Based in: Manchester.
EcommerceGrowth.com works only on Shopify and Shopify Plus, helping ambitious stores improve their email strategy and optimisation. The team draws on more than 20 years of ecommerce experience.
Klaviyo's directory lists it for budgets from under $2,500 a month up to $10,000+, so it is one of the more accessible options on this list.
Klaviyo tier: Platinum Advisor.
Based in: Liverpool, with offices in Leeds and Edinburgh.
Velstar is a Shopify Platinum Partner with more than 120 specialists, working with both DTC and B2B businesses. Klaviyo sits inside its wider technology stack rather than being a standalone service line.
Clients include Castore, Tangle Teezer, Montirex and Sculpted by Aimee, and Velstar reports a 128% year on year revenue increase for Castore.
Klaviyo tier: Gold Advisor.
Based in: Belfast and Dublin.
Glaze Digital describes itself as a specialist Shopify and Klaviyo agency, covering onboarding, strategy, technical development and design, data, and growth work such as SEO and paid media.
It says it has worked with more than 250 stores, which makes it a practical choice for Northern Irish and Irish brands that want both platforms handled by one team.
Traffic costs more every year, so the Shopify brands that grow fastest earn more from each visitor twice: once at the first order, and again every time that customer comes back.
That is why we see ConversionWise and Underground Ecom as complementary partners, not competitors.
We work on the store itself, from landing pages and Shopify development to the tests behind them.
Underground Ecom works on what happens next, through the flows, segments and campaigns that bring a first time buyer back.
If you're not sure where your biggest leak sits, run both diagnostics. A ConversionWise Post-Click Audit shows where visitors drop out before they buy, and an Underground Ecom CRM Impact Session shows where customers drop out after.
Our email marketing guide covers the basics if you're still running Klaviyo in-house.
Book a free CRM Impact Session with Underground Ecom
Underground Ecom is the best Klaviyo agency for Shopify brands in the UK in 2026. It holds Klaviyo's Elite Master tier, won Agency Partner of the Year EMEA 2025, and gives every client a full retention team plus free access to its Underground Insights benchmarking tool.
Elite Master is the highest tier in Klaviyo's service partner programme, above Platinum. Partners are nominated by their Klaviyo partner managers against quantitative requirements, then go through a formal review of qualitative criteria before they are approved.
No. Every agency on this list works with standard Shopify stores, and most also support Shopify Plus. Shopify named Klaviyo the recommended email solution partner for Shopify Plus as part of a 2022 strategic partnership, but standard Shopify stores use the same native integration.
Underground Ecom is the strongest choice for subscription brands, based on its SeoulBox work, where email grew to 41% of total revenue. Thrivelia, whose framework is built around repeat orders, and Email Kong, which builds full lifecycle CRM inside Klaviyo, are good alternatives.
Subscription conversion also depends on the product page. Our own KittySpout case study shows a subscription product page lifting conversion rate 6.84% against the one-time purchase page.
Yes, if both channels matter to revenue, because they fix different halves of the customer journey.
A CRO agency improves how many visitors buy or sign up through landing pages, product pages and checkout.
A Klaviyo agency turns those buyers and subscribers into repeat customers through flows, segmentation and campaigns.
The two teams meet at sign-up forms and post-purchase pages, so agree who owns those before work starts.
Our ROI calculator shows what a conversion lift is worth before you add the repeat revenue on top.
3 more posts in CRO Fundamentals.
