In this article, we consider a prime number theorem for arithmetic progressions “weighted” by Fourier coefficients of modular forms, and we develop Siegel‐Walfisz type and Bombieri–Vinogradov type estimates for such a modular analogue. As an application, we have a Turán type estimate for modular forms asserting that for any δ>0 and non‐CM normalised Hecke eigenform f,
scriptPffalse(a,qfalse)≤q2+δ,with a possible exceptional set of q of density 0 (depending at most on f and δ), where (a,q)=1, scriptPffalse(a,qfalse) denotes the least prime p, with λffalse(pfalse)≠0, congruent to a(modq), and λffalse(pfalse) is the pth Fourier coefficient of f. Moreover, we show the existence of a positive absolute constant C0, independent of f, such that there are infinitely many pairs (p1,p2) of distinct primes satisfying
false|p1−p2false|≤C0andλffalse(p1false)λffalse(p2false)≠0,which presents a modular analogue of the recent work of Maynard and Zhang on bounded gaps between primes.