Solid waste dumpsites receive wastes containing pharmaceuticals and therefore serve as reservoirs of antibiotic residues. Leachates produced from dumpsites are among the principal means of transferring antibiotic residues into the aquatic and soil ecosystems. The occurrence, contamination level and ecotoxicological risk of three fluoroquinolone antibiotics (ciprofloxacin, norfloxacin and ofloxacin) in leachates from three dumpsites in Ibadan, South-Western Nigeria were investigated. An optimized quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction was adopted for the extraction of target fluoroquinolones, extract was cleaned-up by dispersive-solid phase extraction while instrumental analysis was achieved using high performance liquid chromatography (HPLC). Risk quotient approach was used to estimate the potential ecotoxicological risk of target fluoroquinolone antibiotics to aquatic organisms at three trophic levels (algae, daphnid and fish). Recoveries ranged from 102–128%. Method limits of quantification were 0.35, 1.91 and 11.69 μg L⁻¹ for norfloxacin, ciprofloxacin and ofloxacin, respectively. Inter-day precision (% RSD) ranged from 7–22%. High levels of studied fluoroquinolones were quantified, up to 796 μg L⁻¹ for ofloxacin in leachates from Aba-Eku dumpsite. Based on chronic (long-term) toxicity data, norfloxacin in the leachates posed high risk to the three aquatic organisms. Ciprofloxacin presented moderate risk to algae in only Aba-Eku leachate in spite of the low risk observed for daphnids and fish in leachates from the three investigated dumpsites. Considering the high concentrations and potential risk of target fluoroquinolones in the leachates, groundwater resources around the investigated dumpsites should be monitored in future studies for these antibiotics and other pharmaceuticals.