I think there is a pretty big difference but also some overlap. The branding agencies I've worked with provide a "image revamp" so they basically look through your business and its current "image" and current marketing materials and revamp them all, with a new communication message and can possibly recommend you new marketing materials based on your new image.

E.g. they can come in decide that the easiest way to appeal to your target market is to have a more "friendly team image" and therefore help you produce new sales materials with smiling pictures of team members and maybe a new color pallet to "rebrand" what you already have.

You may then want to engage a marketing agency to seed and get more exposure for your new image. This may include things like organising new channels for your message to go out, recommend you places to put print ads, etc.

I think a good analogy to be the difference is if you were a celebrity your branding agency would be your "stylist" and your marketing agency will be your "manager or publicist".

One is there to create your image and the other is to get you out in front of your target market.

Love to hear other people's opinions on this :)

Thanks for asking this great question: I believe there is a difference between a branding agency and a marketing agency but there shouldn't be. My take on branding is the complete ecosystem of a business - its visual assets, communications, customer experiences, online presence, and so on, that shape customer perception. My take on marketing is the planned activity undertaken by an organisation in order to influence customer behavior. They actually go hand in hand. Like two scissor blades you need both to cut. So I link branding and marketing together for good reason. Branding is about customer perception, marketing is about customer behaviour. Perception influences behaviour. I am actually in the midst of writing a book on branding & marketing. Thanks again for asking an insightful question. Regards, Darryn 

Hi Steve, I think there's a big difference between the two. Marketing is more of a push or active promotion of a product or service while branding is the wider spectrum of creating value or identity for a company or organisation.

Glen, so is branding a sub-section of marketing or vice versa? And is active promotion simply a form of advertising?

I respect the diversity of opinion presented in the answers so far. here's my 2c worth and hope it adds to the discussion.

my view is marketing is the strategic activity of researching, planning, implementing and measuring the marketing plan - (unfortunately the use of and therefore definition of the word marketing has been so bastardised over the years that it now means all manner of things to all manner of people)

and branding is a tactical activity (albeit incredibly important) that is centred on your company image, creative positioning, logo and many other components.

personally, i think the strategy and the marketing is more an in-house strategic activity(albeit some smaller companies outsource this to an external person) and branding would usually be an external agency.

branding is the process whereby you visualise the market positioning you choose in your marketing strategy.

i think one company could do both provided they have the skillset within the team to do it.

i've run an outsourced marketing consultancy for 15 years, and worked with companies from $2m to $2b in turnover. i've had internal branding people and also outsourced to them on behalf of clients. both models have been successful for me acting as the CMO for most of my clients and bringing in specialist branding experts as needed. hope this helps you regards hunter

Branding is one part of a marketing strategy, so a marketing agency should deliver brand as part of their remit, while a brand agency wouldn't deliver marketing services. There's definitely some degree of overlap in the strategy area but a branding agency wouldn't advise on your offers and pricing, but they would help you with your positioning, message and reputation build to attract the right people. 
As someone who's spent 20 years in corporate marketing prior to running my own business I can say that the terms 'marketing' and 'brand' are often misunderstood.
Brand is not just visual identity, it's much more about reputation and message. 
Marketing is not just customer acquisition, it's the entire business strategy of building a reputation, attracting, converting and servicing customers, even the end of the customer journey is an opportunity to create a good experience to build brand equity.