The coronavirus (COVID-19) pandemic continues to be a global concern, with over 150 million cases worldwide. Arizona, which was recently a hotspot for COVID-19, has over 860 thousand cases. Reviewing the COVID-19 trends over time is crucial in understanding the pandemic and evaluating the impact of mitigation techniques. This current study analyzes the trends in COVID-19 testing and positivity rates from a mobile testing program in the Phoenix metropolitan area between December 2020 and April 2021. Of the 32,234 tests performed there was a total of 3654 COVID positive cases, yielding an overall positivity rate of 11.3%. COVID-19 positivity rates were significantly higher in December (12.9%) and January (12.7%), compared to February (7.5%), March (4.9%), and April (6.7%), p < 0.05. The peak of COVID-19 cases is likely attributable to the holiday season and family gatherings, followed by a steady decline, likely due to fewer gatherings and an increase in individuals receiving the COVID-19 vaccines. Continued public health measures, including vaccinations, are critical in reducing COVID-19 transmission.