In this article, we present some new inequalities for numerical radius of Hilbert space operators via convex functions. Our results generalize and improve earlier results by El-Haddad and Kittaneh. Among several results, we show that if A ∈ B (H) and r ≥ 2, thenwhere w (·) and · denote the numerical radius and usual operator norm, respectively.2010 Mathematics Subject Classification. Primary 47A12, Secondary 47A30, 15A60, 47A63.