Plant growth can be impacted by ZnO nanoparticles (ZnO-NPs), in addition to their effects on photosynthesis and seed germination. The degree to which nanoparticles (NPs) enhance or inhibit shoot and root growth can vary depending on the specific type of NPs and their concentrations. This research aimed to explore the effects of ZnO-NPs on tomato plants (Solanum lycopersicum L.). The study measured the growth of the plants, their photosynthetic abilities, chlorophyll, physiology responses, antioxidant activities in 24-day-old plants. The results indicated that ZnO-NPs applications improved germination percentage (30.7%), shoot length (47.6%) and root length (33.1%) of the tomato plants, particularly at 75 μg/mL, and enhanced chlorophyll content in a manner proportional to the concentration. Moreover, in current research, it has been found that ZnO-NPs applications improved antioxidant response, and production of antioxidant enzymes. ZnO-NPs also had a beneficial impact on various root parameters including number of root tips (29.6%), number of branching points (16.6%), average diameter (46.2%), branching frequency (26.6%), total root length (33.1%), network area (26.3%), surface area (24.0%), perimeter (22.0%) and root volume (25.2%). Above 75 μg/mL, a reduction in all of them have been noticed, which indicates that concentrations of ZNPs above 75 μg/mL are harmful to tomato plants. Moreover, ZNPs appear to stimulate the transcription of various genes which have antioxidant activities, implying that they may bolster the plant's defense mechanism by enhancing antioxidant enzyme activity. According to our best knowledge, this is a novel aspect to study of impact of ZnO-NPs on root architecture of Solanum lycopersicum L.