The Jc–B performance of MgB2/Fe tapes was enhanced in high magnetic field by the addition of an appropriate amount of nanometre Si3N4 particles. At 4.2 K and in 12 T, the optimum doped samples (1% and 1.67%) show almost twice the value of Jc of that of the undoped tape. The enhancement in the Jc–B performance is considered to come from the introduction of extra pinning centres and the improved core density. It is noted that the dependence of Jc on the magnetic field does not change in different Si3N4 doped samples, indicating that the flux pinning centres introduced by the addition of nanometre Si3N4 particles are limited. Considering the small Tc drop and the residual Si3N4 particles in the heat treated tapes, it is believed that the Si3N4 particles appear as additives in MgB2. The added and/or reaction induced nanometre particles might serve as effective pinning centres.