Yes, you can run Instagram or Facebook ads on Threads without creating new creatives. Meta allows cross-platform ad placements through Advantage+ Placements, automatically delivering existing creatives to Threads if they meet the format requirements.
However, ensure your ads are optimized for Threads' feed and engagement style to maximize performance. If needed, adjust aspect ratios, captions, or CTA elements for better fit. Always review performance metrics to determine if additional creative tweaks are necessary for Threads-specific engagement.