Yes. Radish and Swiss chard have a documented companion-planting benefit. Virginia Cooperative Extension lists swiss chard as a companion for the cabbage-family crop radish.
This is a practical yes, not a magic guarantee. Keep the normal spacing for Radish and Swiss chard, watch airflow and watering, and treat the companion note as one useful planning signal alongside sunlight, soil, and harvest timing.
Source basis: Virginia Cooperative Extension companion planting chart. The page does not add extra pest-control or yield claims beyond the sourced fact row.
Spacing tip: Sow in bands rather than one mixed clump, then thin promptly so roots and leaves have room.