Auditory perception requires categorizing sound sequences, such as speech, into classes, such as syllables. Auditory categorization depends not only on the sequences' acoustic waveform, but also on the listener's sensory uncertainty, any individual sound's relevance to the task, and learning the temporal statistics of the acoustic environment. However, whether and how these factors interact to shape categorization is unknown. Here, we measured human participants' performance on a multi-tone categorization task. Task-relevant tones contributed more to category choice than task-irrelevant tones, confirming that participants combined information about sensory features with task relevance. Conversely, poor estimates of tones' task relevance or high sensory uncertainty adversely impacted category choice. Learning temporal statistics of sound category also affected decisions. The magnitude of this effect correlated inversely with participants' relevance estimates. These results demonstrate that humans differentially weigh sensory uncertainty, task relevance and learning, providing a novel understanding of sensory decision-making under real-life behavioral demands.