The Sydney Swans have reached agreement with the Adelaide Football Club to secure skilled half-back Tony Armstrong, along with selection 35 and a late pick in the national draft.

In exchange for Armstrong and the two draft picks, 20-year-old Swan Lewis Johnston will join the Crows.

The trade will see both players return to their home states.

The deal was finalised this afternoon, with the paperwork to be lodged with the AFL on Monday.

Armstrong, 22, has played 14 games for the Crows and has impressed with his ball use and run off the half back line. The move to the Swans will see Armstrong come home to NSW where he grew up, and where he has family. He played for NSW/ACT at Under 18 level and was taken by the Crows at pick 58 in the 2007 draft.

Swans coach John Longmire said the Club was excited to welcome the silky skilled Armstrong to Sydney.

"With the addition of Tom Mitchell under the father-son rule this week, we think we've got a number of strong inside midfielders at the Club. Tony will bring something else we need, in that he has the ability to run and break the lines and to use the ball well,'' Longmire said.

"It was also important that we were able to get an early second round draft pick (pick 35) from Adelaide and a late selection, so we're happy with the outcome.''

Longmire also thanked Lewis Johnston for the contribution he has made to the Swans since he was drafted in 2008. "Lewis had a foot injury which ruined his early time at the Club but it was a credit to him that he recovered from that and made his senior debut this season. We wish him all the best at the Crows,'' Longmire said.