The Media Square-owned agency won the account following a competitive pitch. It will create SWIM's first campaign to the broader independent financial advisory community.
The trade press and online campaign will break at the beginning of June to coincide with the launch of SWIM's Short-Dated Corporate Bond Fund.
The campaign will appear in selected investment trade press titles and websites, and run throughout the year.
Smith & Williamson provides investment services for private individuals, charities and institutions, with £7.8bn of funds under management and advice. It operates from offices in London, Belfast, Birmingham, Bristol, Glasgow, Guildford and Worcester.
At the beginning of the year, The Gate was appointed by the British Heart Foundation, Cancer Research UK and Diabetes UK to handle the brief supporting the Department of Health's Change4Life anti-obesity campaign.