Good form with the Western Warriors was rewarded with a contract in the 2008 Indian Premier League, where he opened the batting for the Kings XI Punjab. Despite missing the opening four games of the tournament, Marsh scored the most runs in the league stage of tournament, including a century in the final league stage match against the Rajasthan Royals. He received the orange cap for scoring most runs in the 2008 IPL tournament. Shaun Marsh was chosen in the inaugural IPL dream team chosen by the cricketing website Cricinfo along with cricket superstars Sanath Jayasuriya, Kumar Sangakkara, Glenn McGrath and Shane Warne as well as other young talents like Rohit Sharma, Gautam Gambhir and Yusuf Pathan. Marsh has been playing for Kings XI Punjab since the start of the Indian Premier League, becoming one of the most vital players for the team.
He made his debut for Australia in June 2008 in a Twenty20 game against the West Indies alongside fellow West Australian debutant, Luke Ronchi. Opening the batting with Ronchi, they compiled an opening partnership of 57 runs from the first 6 overs, with Marsh being dismissed soon after for 29 runs from 22 balls, including two sixes and a four. He made a memorable One Day International debut a few days later, top scoring for the match with 81 runs from 97 balls and winning the Man of the Match award. With the recent retirements of two of Australia's longest-serving ODI opening batsmen in Adam Gilchrist and Matthew Hayden, Marsh was able to claim one of the opening batsmen positions for the 2008–09 season. In the South African tour of Australia, Marsh performed well in the opening two ODI matches, top-scoring in both matches and winning the Man of the Match award in the second game. He has scored more than 50 in five of his 10 matches, and scored his first century in the 5th ODI against India at Hyderabad on 5 November 2009.
Marsh was included in the Test cricket squad for Australia's tour of India in 2008, but was not selected for a match.