High-frequency sensorineural hearing loss is a common side effect of platinum-based chemotherapies due to the degeneration of cochlear structures. The speech perception of individuals with hearing loss due to chemotherapy has not been as extensively investigated. Studies investigating the speech perception abilities in individuals with hearing loss due to chemotherapy reveal speech perception difficulties and self-perceived hearing handicap greater than expected given pure tone thresholds. This suggests that platinum-based chemotherapies reduce speech perception abilities more than expected given pure-tone thresholds and supports the need for further evaluation of potential underlying mechanisms, such as substantial cochlear damage. The purpose of the present study was to investigate both speech perception abilities and cochlear function in children and adults with hearing loss due to chemotherapy. Speech perception was evaluated for sentence stimuli that were low-pass filtered to create five filter conditions and presented in the presence of speech spectrum noise at three signal-to-noise ratios (SNR). Speech stimuli were presented via digital hearing aids programmed based on the participant's pure tone thresholds. Cochlear function was investigated as a mechanism to identify regions of substantial cochlear damage using Fast Psychophysical Tuning Curves (PTCs) and the Threshold Equalizing Noise (TEN) test. Speech perception and cochlear function were measured in four groups: 30 children and 15 adults with normal hearing, and five children and five adults with hearing loss due to chemotherapy. Participants with hearing impairment generally had poorer speech perception in noise across all filter cut-off and SNR conditions and showed smaller gains in speech perception as the filter-cut off frequency increased when compared to normal-hearing controls. For one child and one adult with hearing impairment, TEN test results demonstrated abnormally high mas (open full item for complete abstract)