The influence of a growth regulator, chlorocholine chloride (commercial name Cycocel 75) on plant growth, (yield) and quality of late-seeded (mid-December) cotton (Gossypium hirsutum) was studied in the Río Dulce Irrigation Area, northwest Argentina, during three growth cycles (1998–2001). Cycocel 75 reduced plant height and node number as well as the total production of aerial biomass, thus increasing the harvest index. Due to an increase in the boll weight and boll number per plant, the yield of treated plots increased by an average of 35% in comparison with the control. Cycocel 75 improved fibre strength significantly, although other parameters of fibre quality, such as length, uniformity, elongation, and micronaire index were not affected. This study indicated that late-planted cotton responds favourably to the application of Cycocel 75, especially when its development cycle is extended due to low air temperatures during the latter part of the growing season.