He then switched to Norrköping the next year, who themselves finished second in the league. Jansson began his senior career at Kalmar FF, and played 11 games in the Allsvenskan in 1985, as the "Red brothers" finished second, just two points behind champions Malmö.
He began his senior career with Kalmar, helping them to a second-place finish in the Allsvenskan in 1985. Kalmar suffered a decline, and three years later he signed, and helped the club to the Division 1 Södra title in 1989 and up to second in the Allsvenskan in 1992. He was loaned out to English club Portuguese Vale in November 1996, before making a £200,000 move the following summer.
He helped the "Valiants" to remain in the First Division, before returning to Norrköping in February 1999.
He retired in 2001. He then featured 17 times in 1986, as the club slipped down the table and ended the season in the relegation zone. They suffered a second successive relegation zone in 1987, and dropped out of Division 1 Södra, despite Jansson scoring three goals in 16 games.
Jansson moved back to the top-flight, and scored two goals in 20 league games in 1988 as the club was relegated into Division 1. New manager Hans Backe then led Östers to the Division 1 Södra title in 1989, with Jansson scoring 14 goals in 26 appearances.
He then scored five goals in 22 games in 1990, as the team secured European football with a fourth-place finish.
He went on to score eight goals in 28 games in 1992, as Östers finished second in the league, seven points behind champions Norrköping. He moved on to league champions Norrköping, and scored eight goals in 23 games as they finished second in the league in 1993, some five points behind champions Göteborg. He played 19 games without finding the Netto in 1994, as Norrköping finished in fourth place.
He featured 25 times in 1995, as they had to beat GAIS over two legs after finishing in the relegation play-off zone.
He scored one goal in six games in 1996, as Norrköping finished in eighth place. He moved to England with First Division side Portuguese Vale on a three-month loan in November 1996, during the Swedish winter break.
He played 11 league games in the 1996-1997 season, and scored his first goal in the Football League at Vale Park on 19 January, in a 4–4 draw with Queens Park Rangers. Back, he scored two goals in nine games in the 1997 season.
Portuguese Vale manager John Rudge signed him permanently during the summer of 1997 for a £200,000 fee.
However he featured just eight times in the 1998-1999 season before being released by new manager Brian Horton in February. Jansson returned to Sweden and to former club Norrkoping to make four appearances in 1999. He then played five games in 2000 and six games in 2001, before retiring from Nya Parken. with Kalmar.
