This research was carried out to determine the effect of potassium fertilization applied at different times and doses in cotton (Gossypium hirsutum L.) on fiber technological properties during the cotton growing vegetation period in 2020 and 2021. The experiment was carried out in randomized blocks in Harran plain conditions according to the split trial design with 3 replications. Fiona cotton (Gossypium hirsutum L.), a variety widely used by farmers, with high bale value in the market, was used as material. In cotton agriculture, the fiber quality and the technological properties of the fiber are closely related to the properties that affect the price for the industry, textile manufacturers and producers, and the increase in these values ​​is also affected by the timely and required dose of plant nutrients. Only nitrogen and phosphorus fertilizers are used in our region where agriculture has been done for many years. As a matter of fact, in the province of Şanlıurfa, which is an important cotton production center of our country, potassium deficiency was detected in places in the observations and soil analyzes made on cotton. According to the results of the research, it was determined that the potassium fertilization doses and timings applied had a statistically significant effect on the fiber length and fiber uniformity ratio in both years, and did not cause a significant difference in the strength and ginning yield characteristics, however, it has been determined that there is an interaction between the application time x application dose in these properties.