N6-methyladenosine (m6A) is the most common eukaryotic internal mRNA modification. Wang et al. show that the m6A reader YTHDF1 promotes the translation of methylated mRNAs in human cells. Transcriptome-wide analyses indicated that YTHDF1 recognizes m6A on many mRNAs. Ribosome profiling revealed a significant decrease in the translation efficiency of YTHDF1 targets following YTHDF1 depletion or the reduction of m6A levels, and tethering YTHDF1 to a reporter transcript enhanced its translation. YTHDF1-dependent translation could be promoted by delivering mRNAs to the translation machinery and by enhancing translation initiation. At mRNAs targeted by both YTHDF1 and YTHDF2 (which decreases mRNA stability), YTHDF1 bound earlier than YTHDF2, suggesting that they function together to dynamically control gene expression.