|Date of birth||29 March 1984|
|Place of birth||Salzburg, Austria|
|Height||1.90 m (6 ft 3 in)|
|2001–2004||Rapid Wien Amateure||13||(11)|
|2004–2005||→ SC Rheindorf Altach (loan)||6||(4)|
|2008||→ Helsingborgs IF (loan)||12||(3)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 28 January 2017.
‡ National team caps and goals correct as of 8 June 2011
Kienast joined the youth team of Rapid Wien at the age of 14. He debuted in the club's first team in 2002. In the next two seasons, he made 24 appearances in the Austrian Football Bundesliga, but was unable to score a goal. In 2004, he was loaned out to SC Rheindorf Altach, then playing in the Austrian Football First League (Austria's second highest professional league). After scoring 4 goals in 6 games, he was quickly called back by Rapid. During the rest of the season, he made 21 appearances for the Vienna side, and finally managed to score his first goal in the Bundesliga. The season ended in glory for the team as they won the Austrian title.
Just before the start of the 2006 season, Kienast came to the Norwegian club Hamarkameratene (Ham-Kam) on loan. He played well during the first spring games, and Ham-Kam decided to buy him. However, he could not prevent the team from going down that season. In the next season, Ham-Kam got promoted back to the Norwegian Premier League, with Kienast playing an integral part in the campaign by scoring 14 goals.
As of 27 May 2008, Kienast has not scored during the 2008 season in Ham-Kam's comeback to the top flight.
On 31 July 2008, Kienast moved to Helsingborgs IF of Allsvenskan in Sweden on loan for the rest of the year with an option for them to buy the player. On 26 November 2013, Kienast scored the first Champions League group stage goal in Austria Vienna's history, netting in the 1:1 away draw with F.C. Porto.
Kienast is a regular in the Austria squad and so far played 10 times for his country. He scored his first senior goal on 27 May with his 1–0 goal against Nigeria in a friendly. After that game, coach Josef Hickersberger chose him in the final squad for the European Championship.
- Austrian Football Bundesliga (2):
- 2005 (Rapid)
- 2011 (Sturm)