It was the away side started on top as on two minutes as Casper Sloth swung in a cross looking for Jermaine Hylton but Blues keeper Gareth Deane came out to collect comfortably.
In a fast paced start to the game David Healy's side created a good opening when Kirk Miller crossed from the right aiming for Jordan Stewart but he couldn't connect with his header allowing the Steelmen to clear.
It was all early Linfield pressure and they caused Motherwell another problem on nine minutes as Matthew Clarke's low cross was well cut out by Richard Tait at the back post.
The Steelman had an effort at goal on 20 minutes as Liam Donnelly tried his luck from range but he blazed his effort over the crossbar from 30 yards out.
Stephen Robinson's side then did take the lead on 28 minutes when Cristopher Long took advantage of a poor back pass from Mark Stafford before taking the ball around Gareth Deane and slotting the ball low into an empty net.
As the Well began to turn the screw they had another good opportunity when Tait crossed for Hylton but Jimmy Callacher beat the summer arrival from Solihull Motors before he could get a strike away on goal.
On the stroke of the break Mark Gillespie made his first save of note when he kept out a header from Mark Stafford after he met a free-kick from Andrew Mitchell but the former Carlisle United and Walsall keeper made a comfortable stop.
It was the Steelmen who started the second half on top as they doubled their lead on 47 minutes when captain Peter Hartley headed into the net following a pinpoint cross from Liam Polworth following a foul from Chris Casement on the impressive Hylton.
It could have been three shortly afterwards Hylton was played in by Long but his effort was well blocked at the last attempt by Callacher when the ball looked set for the net.
Long was then a whisker away from getting his second as his free-kick hit the inside of the post when it looked like it was sailing into the net.
Alex Moore who came on for Gareth Deane at the interval then made an excellent save to keep Linfield in the game on 52 minutes when Long burst into the box before his low cross cum-shot was well parried by the young stopper.
David Healy's men then created a good chance when Trai Hume won a corner after he burst his way into the box before his cross was cut out by Hartley. From the resulting corner Matthew Clarke picked out Lorcan Forde but he bundled his effort wide when he really should have scored.
Less than a minute later it was three for the Steelmen as they broke forward with Danny Johnson before he was taken down by Callacher allowing Jake Carroll's free-kick sailed over the wall and into the top corner beating the helpless Moore on 68 minutes.
Healy's men to their credit didn't let their heads drop and they forced Gillespie into a good save as Humes cross looped towards the top corner but the keeper was alert to to tip the ball over on 72 minutes.
Moore then was alert once again as he made yet another fine save to deny the impressive Motherwell when James Scott skipped past Caomhan McGuinness before his low effort was well kept out by the legs of the stopper.
In what was a comfortable win for Robinson's men they could have had a fourth in the final minute when Johnson pulled the ball back for the onrushing Scott but he dragged his effort wide of the target.