The aim of this study was to evaluate the effects of 60 days of rose-hip and grapeseed dietary supplementation of a balanced home-cooked diet on serum oxidative stress parameters: ROMs, MDA and FRAP in army service dogs before and after regular physical exercise. The dogs were fed a balanced cooked diet as instructed by army standards until the initial blood sampling in June. Thereon the dogs were randomly allotted to 4 groups according to the dietary regime: dogs maintained on a balanced cooked diet according to army standards, branded dry dog food, cooked diet with added 500 mg rose-hip extract, and cooked diet with added 100 mg grapeseed extract for a 60 day period from June to September after which all 4 groups were fed the standard cooked meal diet. Sampling was performed at the beginning of the experiment (June), 60 days from the start of the treatment (September) and finally 60 days after the end of supplementation (November). Statistical analysis of the results included descriptive statistical parameters: mean (M), standard deviation (SD), and variation coefficient (CV%). In order to test the statistical significance of the differences between treatments a multifactor variance test (ANOVA) was performed for ROM, MDA and FRAP and the combined effects of diet, exercise and time period were observed. The initial (in June) increase in MDA and ROMs after exercise indicates the presence of oxidative stress 30 minutes after exercise. However, the antioxidative effects of rose-hip and grapeseed extracts are not conclusive, as multifactor ANOVA testing of time, diet, and exercise factors did not reveal for MDA statistically significant differences either at 60 days of supplementation nor 60 days after withdrawal of the supplements. Only one distinct exception was recorded for the prolonged antioxidative effects reflected in significantly decreased (p<0.01) ROMs before and after exercise in dogs fed the branded dry food 60 days after the end of such dietary regime (November). FRAP values tend to be higher (p>0.05) after exercise compared to before exercise in all experimental groups in November, indicating on a possible redistribution and upregulation of endogenous antioxidants during the experiment.