Background: Plant growth regulators (PGRs) have important roles in many processes such as germination, seedling growth, nutrition uptake, morphogenesis, ripening, etc.

Objective: This study aimed to evaluate the effect of gibberellic acid, indole butyric acid, and methanol as plant growth regulators on morpho-physiological and phytochemical features in Thymus vulgaris L.

Methods: The farm experiment based on a randomized complete block design was performed at 2014. The treatments were included G₁M₁ (GA₃ 50 ppm + methanol 20 %), G₁M₂ (GA₃ 50 ppm + methanol 40 %), G₂M₁ (GA₃ 100 ppm + methanol 20 %), G₂M₂ (GA₃ 100 ppm + methanol 40 %), I₁M₁ (IBA 50 ppm + methanol 20 %), I₁M₂ (IBA 50 ppm + methanol 40 %), I2M1 (IBA 100 ppm + methanol 20 %), I₂M₂ (IBA 100 ppm + methanol 40 %), G₁I₂M₂ (GA₃ 50 ppm + IBA 100 ppm + methanol 40 %), G₁I₂M₂ (GA₃ 100 ppm + IBA 50 ppm + methanol 40 %), and control (distillate water).

Results: The results showed that the combination of GA₃ or IBA along with methanol changed significantly leaf length and width, number of branches, leaf dry weight, stem dry weight, plant dry weight, seed weight, essential oil content and thymol amount. The highest values of the most traits were observed in I₁M₁ treatment.

Conclusion: Methanol combination with one of the GA₃ or IBA can improve morpho-physiological and phytochemical traits of thyme (Thymus vulgaris L.). Thus, the most effective PGRs combination was related to GA₃ 50 ppm + Methanol 20 % and IBA 50 ppm + Methanol 20 %.