The swimwear brand's pan-European advertising business has been with Fallon since 2002, following a pitch against Clemmow Hornby Inge and HHCL & Partners.
The company, owned by Pentland, has been to see a number of agencies and is in the process of drawing up a shortlist. Speedo is said to be considering branding work to increase its share of the lifestyle and leisure apparel market.
The decision to review follows the recent arrival of the brand president, Tony Wood, from Speedo's sister company Berghaus.
The brand's last high-profile advertising, developed in-house, was a global campaign across print, online and outdoor last summer to promote its ties to the Olympics.