The aim of the study was to investigate the effect of cold atmospheric plasma (CAP) and sumac powder (Rhus coriaria L.) on the pH, total soluble solids, color, content of phytochemicals (carotenoids and polyphenols), and microbiological quality of freshly pressed carrot juice. Experiments were carried out with sumac powder concentrations of 0.5 and 3%, which were added before or after 20 min plasma treatment using a gliding arc reactor. The combination of CAP and 3% sumac powder resulted in very effective microbial reduction (to an undetectable level on each day of testing). These juices were characterized by an extended microbiological shelf life of up to 72 h. Additionally, the juice which was first enriched with 3% sumac and then treated with cold plasma, even on the last day of testing, contained 34.36 mg/100 mL of polyphenols and 3.49 mg/100 g more carotenoids than the control samples. The total effect of the application of these method is highly important for the improvement of the quality and safety of carrot juice.