It is the third time Castleford have linked up with their Yorkshire neighbours after similar agreements in 2012 and 2014-15.
Tigers director of rugby Jon Wells said: “We are delighted to enter into a dual registration partnership with the York City Knights for the 2020 season.
“With this partnership and the return of the reserve grade system for next season we can ensure playing opportunities right across all ages and experience levels.
“The two clubs will work closely with one another and we feel this will be a benefit to both.”
As part of the agreement, York’s coaching staff will now have the opportunity to utilise players from Castleford’s full-time environment when they’re not selected for Daryl Powell’s side.
It should prove a valuable asset for the Championship club in allowing them to develop players with further valuable game-time in addition to the Under 18s and Reserves set-ups for 2020.
York last used dual-registration when they were partnered with Hull KR in 2018 during their successful League 1 title-winning season.
Knights head coach James Ford - a former Castleford player - said: “It’s a positive step for us to link up with Castleford. I
“’m confident we can build an excellent relationship where both clubs benefit on and off the field.”