The 28-year-old, who played a key role in helping Plymouth to the League Two play-off final last season, joins the club on a free transfer following the expiry of his contract with the Pilgrims.
Hartley started his career at Sunderland on a youth contract, where he progressed through the ranks and signed his first professional contract in 2006. He made only one first-team appearance for the club, in January 2007, before joining Chesterfield on loan – where he impressed in his 12 appearances for The Spirites.
In 2009, he signed for his hometown club Hartlepool United. It was here that his career really started to kick on, as he made 166 appearances for the club, scoring 10 goals. Hartley also won the Players’ Player of the Year award for his performances in the 2011-2012 League One campaign, as well as winning the League One player of the month award in February 2013.
Following Hartlepool’s relegation in 2013, Hartley returned to League One with Stevenage for an undisclosed five-figure sum. He made 31 appearances for the club, scoring two goals, but was unable to save them from relegation.
In June 2014, he signed for Plymouth Argyle, following his release from a disappointing spell at Stevenage. An impressive first season, in which he made 46 appearances and scored five goals, attracted interest from other clubs – including Scottish Premiership side Ross County – though he opted to remain at Plymouth and battle for promotion from League Two.
Having spent much of the season at the top of the League Two table, a slump in Plymouth’s form led to them missing out on automatic promotion narrowly last time out. Though Hartley scored an emotional last gasp winner against Portsmouth to confirm a play-off final with AFC Wimbledon, they fell to a 2-0 defeat at Wembley.
Rovers latest addition told us "Bristol rovers were the hardest team I played against last season. A strong outfit that I'm very happy to be part of.
"They have an ambitious manager and a very hungry squad with a winning mentality. I can't wait to get going."