[5][6] Mahoney signed with Haukar of the Icelandic Úrvalsdeild kvenna in January 2006, replacing KeKe Tardy.

[10] In the finals she broke Penny Peppas' scoring record by averaging 32.0 points and helped Haukar to a three-game sweep of Keflavík.

On March 6, 2008, the Connecticut Sun traded Mahoney to the Houston Comets in exchange for Barbara Turner.

[15] In 2006 and in 2007, Megan played in Italy with Parma and the next year, she started to play with Cras Basket Taranto and she won the Italian title in 2008/2009 2009/2010 (MVP of the finals) 2011/2012 In 2010–2011, during the Euroleague Women, Mahoney was called in the "Rest of World" team against the Representatives of Europe.

She won the EuroCup Women 2015 and was runner-up the following season, and also came second in the 2014–15 Ligue Féminine de Basketball.

On January 15, 2017, she tore her anterior cruciate ligament of the right knee and missed the rest of the season.