PRWeek understands the decision follows talks with a number of agencies, with one area of focus being drumming up interest from advertisers.
The appointment comes as it emerged last week that the service was in talks with Coca-Cola over the FMCG giant acquiring a shareholding worth £6.2m.
The service has more than 15 million users but is battling in an increasingly competitive market space.
At the end of last week, it emerged at Microsoft would soon enter the market with an Xbox Music service.
PRWeek also revealed on Friday that fellow music streaming business Deezer had called in Blue Rubicon to build its global brand.
Both Spotify and M&C Saatchi PR declined to comment on the deal.