Aims: This work aimed at evaluating the effects of ethanolic and methanolic extracts of lemongrass upon the control in vitro of Colletotrichum gloeosporioides and upon the post-harvest quality of guavas “Paluma”. Methodology: We analyzed the inhibition of mycelial growth and sporulation of the pathogen at different concentrations of the extracts (8%; 5%; 3%; 1.5% and 0.5%). In the post-harvest assay, the guavas were treated by immersion in distilled water, ethanolic and methanolic extracts (1%; 0.5% and 0.25%) and stored at 25ºC ± 2ºC for eight days. We evaluated mass loss, total soluble solids, total titratable acidity, ratio, reducing and non-reducing sugars, ascorbic acid and pH and the incidence of anthracnose. Results: In the test in vitro, the pathogen growth inhibition was dose-dependent and the sporulation was completely inhibited upon higher concentrations of extract. At post-harvest, the fruits maintained their physicochemical characteristics, and the treatments were not efficient at retarding fruit ripening. Although the tested treatments inhibited the plant pathogen C. gloesporioides in vitro, they were not efficient at controlling the disease in vivo. Conclusion: The extracts showed control in vitro of C. gloeosporioides at 8%. However, the extracts were not effective at controlling the disease after harvest.