Animal personality is defined as the consistent expression of behavioural differences between individuals of a population over time and/or across contexts. Although personality is generally assumed to be genetically determined, recent work suggests that social interactions could play an important role in shaping personality traits in social and eusocial organisms. However, it is unclear whether social environment can similarly generate personality differences in non-social species. We examined the effect of social environment on female behaviour in a non-social phasmatid, the Australian spiny leaf stick insect, Extatosoma tiaratum. Social environment was manipulated in the laboratory by exposing mature females to either males or stock females for several weeks. After the pairing period, focal females were separated from conspecifics and subjected to repeated bouts of simulated predator attacks. We found that previous social environment had a significant effect on how females responded to attacks. Exposure to males caused a significant increase in the frequency of certain defensive behaviours (such as feigning death, raising hind legs, kicking, and excreting anti-predator fluids), and many of these male-induced behaviours persisted over time, even when females were no longer paired with males. These results indicate that female personality in spiny leaf stick insects is socially acquired. We discuss our findings in light of recent evidence of sexual conflict in this species.