Botrytis cinereais a necrotrophic fungus characterized mainly by its wide host range of infected plants. The deletion of thewhite-collar-1gene (bcwcl1), which encodes for a blue-light receptor/transcription factor, causes a decrease in virulence, particularly when assays are conducted in the presence of light or photocycles. However, despite ample characterization, the extent of the light-modulated transcriptional responses regulated by BcWCL1 remains unknown. In this study, pathogen and pathogen:host RNA-seq analyses, conducted during non-infective in vitro plate growth and when infectingArabidopsis thalianaleaves, respectively, informed on the global gene expression patterns after a 60 min light pulse on the wild-type B05.10 or ∆bcwcl1 B. cinereastrains. The results revealed a complex fungal photobiology, where the mutant did not react to the light pulse during its interaction with the plant. Indeed, when infectingArabidopsis, no photoreceptor-encoding genes were upregulated upon the light pulse in the ∆bcwcl1mutant. Differentially expressed genes (DEGs) inB. cinereaunder non-infecting conditions were predominantly related to decreased energy production in response to the light pulse. In contrast, DEGs during infection significantly differ in the B05.10 strain and the ∆bcwcl1mutant. Upon illumination at 24 h post-infection in planta, a decrease in theB. cinereavirulence-associated transcripts was observed. Accordingly, after a light pulse, biological functions associated with plant defense appear enriched among light-repressed genes in fungus-infected plants. Taken together, our results show the main transcriptomic differences between wild-typeB. cinereaB05.10 and ∆bcwcl1after a 60 min light pulse when growing saprophytically on a Petri dish and necrotrophically overA. thaliana.