Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by motor neuron loss and declining motor function; however, effective therapies remain limited. To support unbiased therapeutic discovery, we aimed to develop a high-throughput phenotypic screening platform based on a transgenic zebrafish model expressing the human ALS-associated FUS-R521C mutant (mtFUS). This model was generated using a modified QF-based binary expression system and exhibited early-onset pathological features, including elevated oxidative stress, progressive neuronal degeneration, and impaired locomotor activity, thereby recapitulating the key aspects of FUS-associated ALS. Transcriptomic profiling revealed molecular signatures resembling those reported in patient-derived motor neurons, including dysregulated neuroactive ligand–receptor signaling, immune activation, and stress–response pathway alterations. Using this platform, we identified tribenzylamine (TBA) as a candidate compound that improves locomotor performance and significantly reduces reactive oxygen species levels. Integrated transcriptomic and biochemical analyses suggested that TBA induces coordinated molecular changes, including normalization of neuronal activity-related gene expression, modulation of immune and metabolic pathways, and restoration of hormone-related signaling. TBA reversed FUS-induced reductions in key neuronally active sex steroids, including estrogen and progesterone, and increased estrogen-responsive gene expression, suggesting a partial recovery of neuronally active sex steroid homeostasis. These findings support the mtFUS zebrafish model as a useful platform for ALS drug discovery and identify TBA as a candidate modulator of ALS-associated phenotypes, with effects linked to transcriptomic remodeling and neuronally active sex steroid signaling.