The excited Irishman has won the race to confirm Gambian international midfielder Ebou Adams.
According to the Fleet boss, he said no to bigger offers elsewhere so he could sign.
The 22-year-old was being look at by a number of clubs and has played for Dartford and Leyton Orient with great success.
Orient were one of the clubs keen to sign him according to their director of football Martin Ling but Fleet have got in first and the manager is thrilled.
“He’s had similar or better offers elsewhere but he likes what he’s seen here,” McMahon told the club’s website.
“He thinks we’re progressive as a club. He’s coming to us because he’s looked at our squad and how we performed last season and he thinks he’ll be a good fit.
“I think he’ll be a big player for us,” added the Stonebridge Road boss.