The north London side worked hard to capture the defender, as he was on loan at Southampton last season, with the South Coast club having an agreement in place to sign him permanently from Atletico Madrid.
Atletico canceled that agreement, however, and negotiated with Spurs.
And, now that Alderweireld is a Tottenham player, Vertonghen - an old friend of his - took to Twitter to celebrate there being four Belgians at White Hart Lane.
Alongside the defensive duo, Mousa Dembele and Nacer Chadli of Spurs also play for Belgium.
And that makes 4!— Jan Vertonghen (@Jan_Vertonghen) July 8, 2015
Tottenham's official Twitter account responded to Vertonghen's tweet with their own hashtag welcome of the Belgian defender.
Tottenham's gain is no doubt Southampton's loss and it will be interesting to see how the 26-year-old fares at White Hart Lane.
He could be used at centre-back but also as a defensive midfielder. The north London side have clearly been working on sorting out their defence after they leaked goals last campaign. Should they also sign a striker, this can already be considered a summer transfer window that has addressed some key needs for Spurs.