The 26-year-old joined Racing from Chiefs in 2015 and helped them win that season's French title.
His new deal tying him to Racing until 2020 comes in the wake of his two-match suspension for a drunken incident outside a Paris nightclub in October.
Tameifuna spent the night in a cell to sober up after insulting officers on a night out with teammate Viliamu Afatia.
Racing were beaten by their Paris rivals Stade Francais 17-27 last weekend, leaving them fourth in the Top 14 table, six points behind La Rochelle.
They are away to Castres in the European Champions Cup on Saturday.