The premium service enables users to rent programming from British and US broadcasters, with prices starting at 99p for a single episode and rising to £17.99 for an entire series.
The platform has already agreed a deal with MTV Networks for Comedy Central shows such as South Park, and MTV properties such as The Hills, My Super Sweet 16 and Laguna Beach.
A range of BBC Worldwide shows are also now be available to rent, including The Royle Family, Gavin & Stacey, Spooks and Louis Theroux documentaries.
Individual episodes cost between 99p and £1.19 to rent, with a full series costing between £3.99 and £17.99 depending on its size and how recently it has aired on linear TV.
The firm said that "several" other deals are currently in the pipeline with "major Hollywood studios" to offering around 2,000 of premium content in the coming months.
SeeSaw has also tweaked the site's functionality and navigation to enable users to more easily browse available programming. In addition, users can now share SeeSaw links on all the major social networks.
The premium service will run in addition to the 3,000 hours of free-to-view, ad-supported content already available on the site from deals with BBC Worldwide, Channel 4, Five and various UK independent production firms.
"Today's announcement marks the next phase in the evolution of the UK's most exciting online TV service. Since launch, SeeSaw has connected with one million TV lovers across the UK with a mixture of great content, a high quality viewing experience and simplicity of use," said SeeSaw chief executive Pierre-Jean Sebert.
"Going forward, we are confident that our blend of free and premium programming will enhance the appeal of SeeSaw to both viewers and advertisers."
SeeSaw platform controller John Keeling added: "We continue to roll out enhanced functionality and new services ahead of schedule and feedback from users to date has been overwhelmingly positive.
"We look forward to introducing great entertainment content from the major Hollywood studios across the summer months and to giving our viewers what they are asking for."
SeeSaw also said that the site has managed to attract over one million unique users since it launched in mid-February.