Yes. Cabbage and Nasturtium have a documented companion-planting benefit. University of Minnesota Extension cites an Iowa study where marigold, onion, and nasturtium helped reduce cabbageworm damage in cabbage.
This is a practical yes, not a magic guarantee. Keep the normal spacing for Cabbage and Nasturtium, watch airflow and watering, and treat the companion note as one useful planning signal alongside sunlight, soil, and harvest timing.
Source basis: University of Minnesota Extension companion planting guide. The page does not add extra pest-control or yield claims beyond the sourced fact row.
Spacing tip: Use herbs and flowers as edge plantings so they help diversity without competing for the crop row.