Type 2 diabetes (T2D) increases the incidence of colorectal cancer up to three times compared to the population without T2D. Oxidative stress, which is a promoting factor in both conditions, can be efficiently reduced by bioactive compounds from natural sources. Hence, this study aimed to test whether the ethanolic extract of Thymus vulgaris (thyme) tested at 100 μg/mL can act as an effective antioxidant, antidiabetic, and antitumor agent. Plant material was provided by the Institute for Medicinal Plant Research “Dr. Josif Pančić”, Serbia. The antioxidant activity was tested using FRAP assay; the antidiabetic effect was assessed by the level of α-glucosidase inhibition, while the antitumor activity towards colorectal cancer (HCT-116) cell line was determined in MTT, NBT, and Griess assays. In FRAP assay, this sample exhibited comparable antioxidant activity with the one of positive control, BHT (413.03 vs. 576.17 μmol Fe(II)/g dry extract, respectively). Additionally, the extract inhibited 25.91% of α-glucosidase activity, while the standard, acarbose, inhibited 36.76% of α-glucosidase. Although the extract did not influence the viability of HCT-116 cells, it significantly elevated the production of reactive oxygen species (ROS) and nitric oxide (NO) by these cells compared to the untreated control, indicating potential antitumor activity. Finally, thyme ethanolic extract exhibited significant antioxidant and anti-α-glucosidase activities in vitro, as well as ROS- and NO-modulating effects in HCT-116 cells, hence it can be considered as a promising agent for further examination of its action mechanisms in more complex model systems.