Light in the blue region of the spectrum is known to have antimicrobial properties and at sufficient doses it can effectively kill bacterial pathogens, including Escherichia coli. While the killing effect is well established much less is known about how E. coli responds to blue light stress and what protective mechanisms it deploys. In this study we used a range of genetic approaches to look at the genetic factors contributing to the blue light response of E. coli. Mutants from a transposon library that had elevated levels of the stress sigma factor RpoS were found to have increased resistance to blue light treatment. Additionally, culture media that promoted the accumulation of RpoS also conferred protection against blue light killing. The RpoS-regulated DNA binding protein Dps, which is also involved in iron sequestration, was found to play a critical role in protecting against the DNA-damaging effects of blue light; mutants lacking this protein were extremely blue light sensitive and exhibited more DNA damage than the parental strain when light exposed. We hypothesise that blue light induces oxidative stress leading to DNA damage and that both RpoS and Dps can protect against this. Indeed, cells pre-exposed to oxidative stress were more resistant to blue light stress, and the reverse was also true, cells exposed to blue light acquired resistance to oxidative stress. Collectively these findings demonstrate that oxidative stress and DNA damage occur in E. coli during blue light exposure and RpoS and Dps protect against blue light by mitigating these effects.