The fifth and final season of Tubridy Tonight commenced airing on 27 September 2008 and completed broadcasting on 30 May 2009. The series, hosted by Ryan Tubridy, aired on RTÉ One on Saturdays nights following the RTÉ News: Nine O'Clock. At the end of this series, Tubridy took over from Pat Kenny as host of The Late Late Show on Friday nights on the same channel.
Musical guests throughout the series included Fall Out Boy, The Saturdays, Sugababes, Gabriella Cilmi, Take That, The Script, Lady GaGa, Petula Clark, Bell X1, The Blizzards, Dolores O'Riordan, Boyzone, Melody Gardot and Spandau Ballet.
This series featured a new set, retaining its traditional library theme but updated for the 21st century. The opening episode featured Aidan and Marian Quinn, who spoke of their film 32A, and actresses Charlene McKenna and Shelley Conn who spoke of their parts in Raw. Don Baker also spoke of his time on Fáilte Towers, whilst there were comedic and musical performances from Oliver Callan and Fujiya & Miyagi respectively.
The second episode featured the Seoige sisters, Gráinne and Síle, who were about to launch their new television series, Seoige. Also appearing were actress Anna Faris to talk about her film, The House Bunny, and Peaches Geldof who was quizzed on how her father Bob reacted to her Las Vegas wedding. The third episode featured the three times Eurovision winner Johnny Logan, author Jackie Collins, comedian Paddy Courtney, and model and wife of Claudine Palmer, Robbie Keane. Tubridy was said to be hoping that Collins would "spill the beans on the excesses of Tinseltown's glory days".
Guests on the fourth episode included At Your Service hoteliers Francis and John Brennan and actor Michael Fassbender who Tubridy described as "a really talented Irish actor and his performance in the new Bobby Sands film Hunger is fantastic, there are definitely big things in store for him". Before his appearance on the fifth episode, Tubridy described Mike Murphy as "one of my all-time heroes" and "an Irish broadcasting legend". Tubridy also described himself as a fan of the Eoin Colfer novel series, Artemis Fowl, and Sugababes song "Girls" before the writer and band both appeared on episode six.
The seventh episode featured director Richard Attenborough, Desperate Housewives''' actor Dougray Scott and Irish television personalities Zig and Zag, whose last television appearance was on 1990s chat show Kenny Live and who referred to Tubridy as "Twiggery" throughout. In the ninth episode, golfer Pádraig Harrington granted his first major television interview since winning both the year's British Open and PGA Championship. Also appearing in this edition were television presenters Eamonn Holmes and Ruth Langsford, as well as actor John Slattery from Mad Men, Desperate Housewives, Sex & the City and Will & Grace. Comedian Dara Ó Briain, rugby union players Anthony Foley and Peter Stringer and actor Aidan Gillen (The Wire) featured in the tenth episode.
Stylist Gok Wan was interviewed in the eleventh episode, which also featured reformed British boyband Take That - the show was inundated with audience ticket requests by fans of the band when it was announced they would be appearing. The Script flew in especially to appear on the thirteenth episode.
The fifteenth episode was also the first of 2009 and featured Tom Chambers, Craig Revel Horwood and Bruno Tonioli from the BBC's Strictly Come Dancing and Mark Hamilton from RTÉ's How Long Will You Live? series. Actor Roger Moore was a guest on the sixteenth edition of the fifth series, with Tubridy commenting beforehand that he was "a huge Bond fan and... ...loved all his 007 performances". Moore spoke about his acting career as well as his time spent as an ambassador with UNICEF, whilst fellow guest Maura Derrane spoke of her role presenting the TG4 television series Feirme Factor. The eighteenth edition featured actor William Shatner who discussed his roles on Star Trek and Boston Legal, and La Toya Jackson who spoke of her time spent on the UK television series Big Brother.