This study was conducted in Msilale Village, Chato District in Tanzania, to evaluate the influence of sowing dates and phosphorus levels on cotton fiber quality. The study was established according to a factorial trial, with varying sowing dates (25(th) November 2022, 15(th) December 2022 and 4(th) January 2023) and phosphorus levels (control, 20 kg P ha(-1), 40 kg P ha(-1), 60 kg P ha(-1)). Results revealed that early planting had a statistically significant (p < .001) effect on fiber cotton quality, including spinning coefficient index, fiber length, fiber strength, uniformity index, short fiber content, and grade/color. Early sowing dates (25(th) November 2022 and 15(th) December 2022) consistently produced superior fiber quality, including spinning coefficient index (156.5 and 148.4), moisture content of the fiber (7.8% and 7.7%), micronaire (3.5 mu g/inch), upper half mean length (1.2 cm), uniformity index (84.6% and 84.2%) and shorter fiber (6.8% and 7.0%) relative to late sowing (4(th) January 2023). Conversely, phosphorus levels did not significantly (p > .05) impact these parameters within the tested range. This research underscores the critical role of selecting appropriate sowing dates for cotton cultivation to achieve better fiber quality.