<p>Biochar application is widely promoted as a soil amendment to enhance soil fertility. However, significant knowledge gaps persist regarding its effect on herbicide efficacy and its impact on non-target organisms in tropical agroecosystems. This study aimed to evaluate, under laboratory and greenhouse conditions using a tropical Ultisol, how the addition of pyrolyzed carbonaceous materials influences (i) the efficacy and environmental behavior of the herbicides bromacil and diuron, and (ii) the response of soil fauna bioindicator species and microbial functional diversity. Pineapple stubble and coffee hulls, pyrolyzed at 300° (torrefied materials) or 600&#xa0;°C (biochar), were used. These materials were applied at two rates (10 and 20 t ha^− 1), both with and without the application of bromacil and diuron. Evaluations included herbicide phytotoxicity, plant growth, survival and reproduction of soil fauna (Collembola and Enchytraeids), soil avoidance/preference behavior, and microbial functional diversity. The addition of carbonaceous materials did not affect the phytotoxicity of the herbicides or initial plant growth in the absence of herbicides. The survival of non-target fauna species was also unaffected; conversely, their reproduction was consistently promoted. However, a contrasting ecotoxicological response in behavior was observed: while Enchytraeids showed a generalized avoidance of the amended soil, Collembola exhibited a marked preference. Soil microbial functional diversity remained largely unaltered. Pyrolyzed carbonaceous materials did not compromise the efficacy of the herbicides or the survival of non-target soil organisms. Nevertheless, alterations in faunal behavior suggest a selective ecological influence. Despite the observed benefits in promoting faunal reproduction, further field studies are required to better understand the long-term effects of these materials on the ecological dynamics of tropical agroecosystems.</p>