Grimsby striker Michael Boulding has signed for Barnsley for an undisclosed fee. Reds striker Isaiah Rankin has gone in the other direction on a month's loan.
Boulding handed in a transfer request after the departure of Mariners manager Paul Groves.
Gudjon Thordarson said: "Michael completed his agreement with Grimsby and we are now to discuss personal terms - we're more or less completing those now.
"We're very pleased to have finally got him here. It's another good deal for the club.
"Isaiah Rankin will be going the other way for a month on loan as part of the agreement, but Boulding is a permanent signing on a two-year contract."