Auxin response factors (ARFs) are critical components of the auxin signaling pathway, and are involved in diverse plant biological processes. However,ARFgenes have not been investigated in flax (Linum usitatissimumL.), an important oilseed and fiber crop. In this study, we comprehensively analyzed theARFgene family and identified 33LuARFgenes unevenly distributed on the 13 chromosomes of Longya-10, an oil-use flax variety. Detailed analysis revealed wide variation among the ARF family members and predicted nuclear localization for all proteins. Nineteen LuARFs contained a complete ARF structure, including DBD, MR, and CTD, whereas the other fourteen lacked the CTD. Phylogenetic analysis grouped the LuARFs into four (I–V) clades. Combined with sequence analysis, the LuARFs from the same clade showed structural conservation, implying functional redundancy. Duplication analysis identified twenty-seven whole-genome-duplicatedLuARFgenes and four tandem-duplicatedLuARFgenes. These duplicated gene pairs’ Ka/Ksratios suggested a strong purifying selection pressure on theLuARFgenes. Collinearity analysis revealed that about half of theLuARFgenes had homologs in other species, indicating a relatively conserved nature of theARFs. The promoter analysis identified numerous hormone- and stress-related elements, and the qRT-PCR experiment revealed that allLuARFgenes were responsive to phytohormone (IAA, GA3, and NAA) and stress (PEG, NaCl, cold, and heat) treatments. Finally, expression profiling ofLuARFgenes in different tissues by qRT-PCR indicated their specific functions in stem or capsule growth. Thus, our findings suggest the potential functions ofLuARFsin flax growth and response to an exogenous stimulus, providing a basis for further functional studies on these genes.