Saccharina latissima is a brown algal kelp species of ecological and economic importance. As the rise in sea surface temperature will threaten not only wild populations of S. latissima but also the productivity of kelp farms, crop enhancement techniques will become crucial to mitigate this threat. Priming is a common strategy in crop plants, in which seeds are pre-exposed to a moderate stress to improve the performance and tolerance of plants when exposed to harsher conditions. We investigated the potential of thermal priming to improve growth and tolerance of S. latissima. Kelp gametophytes primed at 20°C for 2, 4 and 6 weeks and then re-transferred to 5°C were compared to a naïve treatment maintained at 5°C. Gametophytes priming increased growth of subsequently formed sporophytes by up to 30% (for 4 weeks priming) compared to the naïve treatment. Female gametophyte growth in the priming environment was positively correlated to offspring sporophyte growth, indicating a maternal effect. Sporophytes were exposed to a heat stress of 20, 22, 23 and 24°C for two weeks. Sporophytes from 4- and 6-weeks primed gametophytes exhibited 11 days longer tolerance at 22°C, 7 days longer tolerance at 23°C and 1°C higher thermal tolerance over 7 days compared to naïve sporophytes and sporophytes from 2 weeks priming. A priming time of 4 weeks was optimal for both sporophyte growth and thermal tolerance. Our results suggest that priming is a promising crop enhancement technique that could improve yield for seaweed farmers and restoration of kelp forests threatened by warming climates.