A novel granulated L-methionine (Met) has been developed using a simplified purification process, however its replacement with DL-Met has not yet been explored. The objective of the present study was to investigate the growth performance of broilers fed diets containing granulated L-Met (90% purity) compared to a diet containing DL-Met (99% purity). A total of 192 one-day-old broilers were allocated in four dietary treatments with six replicates (eight birds/cage) in a randomized complete block design based on body weight as the blocking factor. Twelve experimental diets were used, with four for each of the three growth stages: pre-starter (day 0 to 7), starter (day 7 to 21), and grower (day 21 to 28). The experimental diets consisted of: (1) a diet containing DL-Met at 100% of the digestible Met requirement, (2) a diet containing granulated L-Met at 85% of the digestible Met requirement, (3) a diet containing granulated L-Met at 90% of the digestible Met requirement, and (4) a diet containing granulated L-Met at the same inclusion rate (approximately 95% of the digestible Met requirement) as diet 1. The broilers were fed experimental diets during the pre-starter, starter, and grower stages, and growth performance was recorded by correcting mortality throughout the experiment period. Over the entire 28-day period, body weight gain and feed intake of broilers fed diets containing granulated L-Met increased linearly ( < 0.05) with an increase in dietary granulated L-Met supplementation. However, the growth performance of broilers fed diets containing granulated L-Met did not differ from those fed a diet containing DL-Met. The bioefficacy of L-Met relative to DL-Met for body weight gain and gain-to-feed ratio during the pre-starter stage was 116.9% and 104.0%, respectively. During the starter stage, the bioefficacy of L-Met relative to DL-Met was 127.5% and 111.0% for body weight gain and gain-to-feed ratio, respectively. Results of the present study reveal that the growth performance of broilers fed diets containing granulated L-Met was comparable to those fed a diet containing DL-Met, despite the lower dietary Met intake than digestible Met requirement. This suggests that L-Met might exhibit greater bioefficacy relative to DL-Met.