About

About Tristan Gillen

Tristan Gillen is a Lisbon-based fractional CMO for startups and startup growth advisor who has built growth teams and go-to-market strategies for over 100 startups. He is the co-founder of GREX, an AI growth operating system, and Growth Division, a B2B growth agency.

Originally from the UK and now based in Lisbon, I specialise in scaling startups in the UK, Europe and the US. The subject I've gone deepest on is the startup growth process: how a team decides what to test, measures it, and turns what works into a repeatable growth engine.

Tristan Gillen, fractional CMO, Lisbon

At a glance

Role
Fractional CMO & startup growth advisor
Based in
Lisbon, Portugal (from the UK)
Markets
UK, Europe, US
Experience
10+ years, 100+ startups
Companies
GREX (co-founder), Growth Division (co-founder)
Expertise
Go-to-market strategy, growth teams, growth experiments, customer acquisition

My story

Quick story. Straight out of university, my long-term business partner Tom Dewhurst and I built a mobile ordering and payment app. We raised money, scaled it to tens of thousands of users and partnered with some properly big brands. I learnt more in those years than in anything since, mostly the hard way.

Since then I've worked with over 100 startups: as a founder, on founding teams, as a consultant and through Growth Division, the startup growth agency Tom and I run. We help startups find and validate their channels to market, and along the way I've worked with the likes of Startups.com, SeedLegals, Oddbox and Weavr.

Not everything works, and honestly that's the most useful bit. At Startups.com, cold email was hard to justify on ROI, so we stopped it and switched to LinkedIn outreach, which converted at 10%. At Eat Sleep Cycle we ruled out Meta ads as a scalable channel altogether. Knowing what to cut is half the job!

The startup growth process is the subject I've gone very DEEP on. So deep, in fact, that I'm now building GREX, an AI growth operating system that turns that process into software. And when I'm not doing that, I run Business on Boats (BoB to its friends), a fun boat booking business here in Lisbon.

My career

  1. 2015 to 2019

    Co-founded a mobile ordering and payment app

    Straight out of university, with long-term business partner Tom Dewhurst. Raised investment, scaled to tens of thousands of users and partnered with globally recognised brands.

  2. 2019 to now

    Co-founded Growth Division

    A startup growth agency that helps startups find and validate channels to market through a community of growth experts. Worked with the likes of Startups.com, SeedLegals, Oddbox and Weavr.

  3. 2019 to now

    Fractional CMO and growth advisor

    Over 100 startups helped across the UK, Europe and the US, as a fractional CMO, advisor and growth lead.

  4. 2026 to now

    Co-founded GREX

    An AI growth operating system that turns the startup growth process into software.

GREXGrowth DivisionBusiness on Boats

Selected results

See all case studies

Speaking & writing

I regularly speak at events and on podcasts and write guest posts. Topics I speak about:

  • How startups should build their go-to-market strategy
  • How to form your startup growth team
  • How to run Growth Marketing Experiments
  • Reasons why startups fail to grow

Previous contributions

Press kit

For event organisers, journalists and anyone writing about fractional CMOs. Please use these as written.

One-line bio

Tristan Gillen is a Lisbon-based fractional CMO and startup growth advisor who has built growth teams and go-to-market strategies for over 100 startups.

Short bio

Tristan Gillen is a fractional CMO and startup growth advisor based in Lisbon, Portugal. Originally from the UK, he has spent over 10 years building growth teams and go-to-market strategies for more than 100 startups across the UK, Europe and the US, as a founder, founding team member, consultant and co-founder of the startup growth agency Growth Division. He is now building GREX, an AI growth operating system. He speaks regularly on go-to-market strategy, growth teams and growth experiments, including for Seedcamp, Partech and Unicorn Factory Lisboa.

Photos

Logos, colours and fonts are on the brand assets page. Contact: tristan@growth-division.com

Things I love

Environment

I want to leave this planet a net contributor. We only get the one, and I think we all have a responsibility, as individuals and as businesses, to leave it in better shape than we found it. So I contribute where I can, using the experience and assets I've built up to help others and the planet.

See more about my contribution

Coffee

Coffee is one of life's great pleasures. I'm always trying new beans and new roasters, whether I'm brewing on the Aeropress, V60, Chemex, French press or Moka pot. My brother and I keep notes on every one in a shared Notion board (yes, really!), and you can have a nose at it below.

See what I'm drinking now

Reading

Every year I set myself a reading challenge. It's my favourite way to switch off and learn something at the same time, and I flip between fiction and non-fiction depending on my mood. All my reviews are on GoodReads if you fancy following along.

See what I'm reading at the moment

Drum and Bass

I've been massively into drum and bass for years, and I'm forever trying to convert people. Give me a follow on Spotify for a very extensive collection of DnB playlists...

See what I am listening to

And that's me!

Let's have a coffee?

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