Jamar was drafted at pick number six to Melbourne in the 2001 Rookie Draft. He debuted in the opening round of the 2003 season against, which the Demons won by six points. He had a quiet debut with only four disposals, a mark and a hit-out on the stats sheet. However he improved in his next match, a 27-point win over in which he registered six disposals, 10 hit-outs and his first AFL goal. He went on to play another seven games that season, all of which Melbourne lost. They finished 14th and did not play in the finals. Jamar ranked fourth among rising stars in total hit-outs in 2003 and third among rising stars in hit-outs per game in 2003. Jamar only played three games in 2004, including an elimination final that the Demons lost in a five-point match against Essendon. He averaged five disposals and seven hit-outs. In 2005, Jamar played eight games - of which the Demons won five of. He averaged only three disposals and eight hit-outs and kicked one goal in the ruck. Melbourne finished seventh and played in the elimination final against, which they lost by 55 points. Jamar missed only one game in the whole 2006 season. He consolidated himself as a reliable ruckman for the Demons. He averaged 10 hit-outs and four disposals and kicked 10 goals and two behinds for the season. Melbourne finished the season seventh and played in the elimination final, which the Demons won by 18 points. Jamar contributed in the ruck with seven hit-outs and four disposals. He did not play against the following week when the Demons were defeated by 28 points and were eliminated from the finals. In 2007, Jamar missed the middle part of the season, but played the first and last five games of the season. He only played in two winning matches and averaged 6 disposals and 10 hit-outs as well as kicking four goals for the season. The Demons finished 14th. In 2008, Jamar played 14 games and averaged eight disposals and 19 hit-outs and kicked four goals. Though Melbourne finished last and did not qualify for finals, Jamar had made himself known in the AFL, performing reliably in the ruck. He ranked ninth in hit-outs per game for 2008. A stress fracture in his foot resulted in Jamar missing much of the 2009 season. In the games he did play he played in the primary ruck position, averaging 23 hit-outs and 11 disposals. Once again the Demons finished bottom of the ladder, but Jamar's efforts as Melbourne's main big man did not go unnoticed. He was ranked seventh in hit-outs per game for the year. Jamar went from strength to strength as Melbourne's number one ruck in 2010, playing an instrumental part in the Demons' rise up the ladder, averaging 29 hit-outs, 12 disposals and three contested marks per game, with four goals over the first seven rounds. He was ranked second in the AFL for hit-outs per game, was named as the second ruckman for the 2010 All-Australian squad and finished third in Melbourne's Best and Fairest, behind Brad Green and James Frawley. He was informed in September2015 that he would not be offered a contract from Melbourne for 2016, effectively ending his fourteen-year career with the club after 155 games. In December 2015, Jamar announced that he had signed to play with St Kevin's Old Boys in premier division of the Victorian Amateur Football Association for season 2016. In February 2016, Jamar signed with Essendon due to the club's supplements controversy.
