Du, G.-H., Liu, F.-H. and Rowland, G. 2015. Fiber cell development and fiber yield of flax (Linum usitatissimum L.) affected by the seasonal temperature pattern. Can. J. Plant Sci. 95: 1215-1220. Three fiber flax cultivars ‘Ariane’, ‘Argos’ and ‘Viking’ were cultured in growth chambers under three seasonal temperature patterns (STPs) [parabolic (P), anti-parabolic (AP) and quasi-horizontal (QH) configurations]. The effect of STP was studied on fiber cell development and on fiber yield. The results indicated that, compared with the quasi-horizontal seasonal temperature pattern (QH-STP), the size of fiber cell cavity (SFCC) and fiber content (FC) decreased under parabolic seasonal temperature pattern (P-STP). However, the size of fiber cell (SFC) and SFCC decreased, but the number of fiber cells per bundle (NFCB) increased under anti-parabolic seasonal temperature pattern (AP-STP). Moreover, there was a significant positive correlation between fiber weight (FW) and width of fiber bundle (WFB), also between FC and NFCB. Considering the response of fiber flax cultivars to the different STPs, ‘Ariane’ had smaller SFC and SFCC, thinner thickness of fiber cell wall (TFCW) under AP-STP, and smaller SFCC and thicker TFCW under P-STP than under QH-STP, while ‘Argos’ had smaller SFC and SFCC, and higher NFCB under AP-STP, and smaller SFC under P-STP than under QH-STP. However, STPs had little effect on the fiber cell development of ‘Viking’. All three cultivars had high FC under AP-STP than under P-STP. These observations indicate that the fiber cell development and fiber yield of flax were related to the STP and suggest that AP-STP are the most favorable temperature conditions for fiber flax growth.