The study evaluated the effects on the growth performance and carcass characteristics of broiler chickens of DL-Methionine (DL-Met) and methionine hydroxy analogue (MHA) supplementation and their partial replacement with betaine (Bet). Two experiments were performed from day 1 to 21 and from day 22 to 42. Broiler chickens were assigned to six treatments, in a completely randomized design and a 2 × 2 + 2 factorial arrangement, consisting of two Met sources (DL-Met and MHA), with or without Bet, and two negative controls. The six treatments consisted of i) NC-DLM: negative control for DL-Met with 7% reduction in DL-Met; ii) NC-MHA: negative control for MHA with 7% reduction of MHA, iii) DLM100: without Bet, supplemented exclusively with DL-Met reaching 100% of requirements, iv) MHA100: without Bet supplemented exclusively with MHA reaching 100% of requirements, v) DLM93+Bet: DL-Met at 93% of recommended level plus betaine; vi) MHA93+Bet: MHA at 93% of recommended level plus betaine. Growth from day 1 to 21 was not altered by methionine source or betaine supplementation. However, the negative controls had numerically less weight gain and feed conversion ratio (FCR) . Between days and 42 there were no effects on growth. Betaine could partially replace methionine without altering the growth of broiler chickens. In addition, the partial replacement of DL-Met with betaine increased body crude protein content. However, its use increased body fat content regardless of methionine source.