A retention marketing agency runs the channels that bring customers back after the first order: email, SMS and the flows behind them, and for subscription brands the cancel flow and failed payments too. Every agency here is a Klaviyo partner, and each entry says who it suits.
The shortlist at a glance
| Agency | Good fit for | Klaviyo listing |
|---|---|---|
| Email Kong | Shopify brands where repeat orders drive the business, subscription brands included | Master Platinum |
| Sticky Digital | Shopify brands on Recharge that want a retention-only agency | Master Platinum |
| The Email Marketers | 8-figure brands that want email, SMS, direct mail and loyalty | Master Platinum |
| Flowium | Brands that want an email-first programme from a large agency | Master Elite |
| Chronos Agency | Brands over $10M a year that want direct mail with email and SMS | Master Elite |
| Structured | Established DTC brands that want email and SMS specialists | Master Platinum |
| Magnet Monster | Several channels run by one small team | Master Elite |
| Underground Ecom | Large brands that want retention plus acquisition | Master Elite |
1. Email Kong
We're a retention agency for Shopify brands in the UK and US, and most of our clients sell subscriptions or products people buy again. We run the whole Klaviyo account: the campaign calendar, design, copy, flows and SMS. For subscription brands we also work inside Loop, Appstle and Checkout Champ on the cancel flow, save offers, failed payment recovery and winback, which is where most subscribers are lost.
We're a Klaviyo Master Platinum Partner, ranked in the top 2.5% of partners worldwide, and a Loop Platinum Partner. Our founder, Bogdan Mihalache, is a member of the Klaviyo Partner Advisory Council, one of 35 members worldwide. Over 5 years we've worked with 140+ DTC brands and driven $59M+ in revenue attributed to Klaviyo at a 65.2x average ROI, and we're rated 4.5 on Trustpilot.
Kaori went from saving 4.3% to 60% of subscribers who tried to cancel, and from 3.3% to 19% of store revenue coming from Klaviyo. Penrose Skin went from saving 9% to 38%, and from 15.2% to 23.2% of revenue from Klaviyo while the store more than tripled. At KittySpout, 46% of revenue is attributed to Klaviyo.
We're an AI-first retention agency, with about 120 flow A/B tests live across our clients. Your first flow is live within 72 hours of us getting access, and after that every month runs on the EK Retention Cycle: fix what's leaking, test it, keep what wins. For brands that bill through Checkout Champ, we built our own event bridge that brings rebills, declines, cancels and pauses into Klaviyo. You get a shared Slack channel, a monthly report and call, and a reply within 1 working day. Retainers start from $5,000 a month.
Good fit if: repeat orders drive your business and you want one senior team that owns Klaviyo and your subscription app.
2. Sticky Digital
Sticky Digital is a Klaviyo Master Platinum partner that works only on retention for Shopify brands, through email and SMS. Recharge's partner directory lists its expertise in the Recharge API, flows, bundles, loyalty, SMS and the customer portal. Clients include U Beauty, MUD\WTR, Nest New York, r.e.m. beauty and Xmondo.
Good fit if: you sell subscriptions on Recharge and want a retention-only agency.
3. The Email Marketers
The Email Marketers is a Klaviyo Platinum Master partner for 7 to 9-figure ecommerce brands, with its sweet spot in the 8-figure range. It runs email, SMS, push, direct mail, subscriptions, memberships, loyalty and referral, and it publishes its own research from 109 Klaviyo audits. Clients include Llama Naturals and Kick Game.
Good fit if: you're an 8-figure brand and want loyalty, referral and direct mail run with your email and SMS.
4. Flowium
Flowium is a Klaviyo Master Elite agency in North America that says it has worked with 1,000+ brands since 2017. It runs email-first lifecycle programmes and adds SMS, WhatsApp, RCS, Instagram DM automation, push and direct mail as needed. Clients include Dr. Squatch, True Classic, Last Crumb, RSVLTS and Sky Zone.
Good fit if: you want an email-first programme from a large, established agency.
5. YOCTO
This Klaviyo Elite partner works with subscription-first brands in health, wellness, supplements and beauty, and its team works every day in Loop, Recharge and Skio. It covers the cancel flow, failed payments and the Klaviyo flows around them. Clients include Healf, Evereden and MiraCare.
Good fit if: you're a larger subscription brand and want a team that knows all 3 big subscription apps.
6. Chronos Agency
Chronos is a Klaviyo Master Elite agency that says it works with 500+ brands. It runs email, SMS, push and direct mail for brands of $10M to $500M a year across beauty, apparel, wellness, home, food and pet. Clients include The Oodie, Organifi, Kiyoko Beauty and Qure Skincare.
Good fit if: you're over $10M a year and want direct mail with your email and SMS.
7. Structured
Structured is a Klaviyo Master Platinum email and SMS agency with a team of about 80, working with 100+ DTC brands. Clients include Eight Sleep, Fly By Jing, Health-Ade, Poo~Pourri, Hydrant and Mixtiles.
Good fit if: you're an established DTC brand and want an email and SMS specialist.
8. Magnet Monster
Magnet Monster is a Klaviyo Master Elite agency, small by design, with offices in Sale, Cheshire and Singapore. It runs email, SMS, WhatsApp and direct mail, focuses on unit economics and offers a subscription audit. Clients include Waterdrop, Laura Geller, Wild and Outerknown.
Good fit if: you want several channels run by one small team.
9. Underground Ecom
Underground Ecom is a UK retention agency and Klaviyo Master Elite partner, and its listing says it was Klaviyo Agency of the Year 2025. It runs email, SMS, WhatsApp and push alongside SEO, paid media and subscriber growth. Clients include AG1, Huda Beauty, Osprey and Simba Sleep.
Good fit if: you're a large brand that wants retention and acquisition from one agency.
How to choose
- Can they show results from brands that sell like you do, subscription, replenishment or one-off?
- Will they work inside your subscription app, loyalty and reviews tools, or only in Klaviyo?
- Who actually does the strategy, copy, design and builds?
- Can they show Klaviyo's share of store revenue before and after, with dates?
- What's in the monthly scope, and what's the minimum term?
For a Shopify-only view, see the best retention agencies for Shopify brands. If you sell subscriptions, read the best Klaviyo agencies for subscription brands. If you want a UK team, see the best Klaviyo agencies in the UK and the best Klaviyo agencies in London.
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Sources
- Email Kong: Klaviyo directory, Loop directory
- Sticky Digital: Klaviyo directory, Recharge directory
- The Email Marketers: Klaviyo directory, website
- Flowium: Klaviyo directory, website
- Chronos Agency: Klaviyo directory
- Structured: Klaviyo directory
- Magnet Monster: Klaviyo directory, website
- Underground Ecom: Klaviyo directory, website
