A dubious early penalty to Welling kept Eastbourne Borough on the back foot throughout this Blue Square South clash.
Welling, who secured their play-off spot thanks to their 3-0 win, went ahead after 13 minutes.
Ollie Rowe was harshly judged to have handled in the box and Joe Healy scored emphatically from the spot.
The highflying visitors increased their lead on 23 minutes when Loick Pires nodded home Healy’s centre.
Boro’ so nearly hit back two minutes later when Gary Hart’s looping effort came back to Watson and his shot cannoned off the post.
Welling stamped their authority on the match after the break. Harry Baker embarked on a fine run and Pires was denied by a sublime save from Mitch Walker.
The third goal arrived on 71 minutes. Alex Lacey was caught in possession at the back and Pires ran through and scored beyond Walker.
Boro: Walker, Hamilton Omole (Brinkhurst 72), Lacey, Rowe, Cole, Johnson, Anderson, Smart (Mason 76), Ademeno, Hart, Watson (Remy 52)
See Wednesday’s Gazette for full match report and reaction