In 2001 she married Sylvia Knight. In 2007 she underwent gender reassignment surgery. In 2009, Sarah and Sylvia divorced and then formed a civil partnership. 
Sarah Brown was placed number 28 on the Independent on Sunday Pink List 2011, and was the highest-ranking transgender person on the list.
Her favourite hobby is rock climbing.
In 2013 she was reported to be in a polyamorous relationship with Knight and fellow Liberal Democrat and transgender activist Zoe O'Connell, although none of them describe themselves as "poly evangelists". All three partners contributed to a Guardian column discussing polyamory in the context of transition and Brown's previous marriage, which was later cited by her local MP during the Marriage (Same-Sex Couples) Bill debate.
- Patrick Barkham, "'Why three in a bed isn't a crowd' - the polyamorous trio" The Guardian 20 April 2013