Authorities in Davangere, Karnataka, arrested 20-year-old Suhail, a native of Uttar Pradesh, over suspected terror links.
The arrest followed an NIA-led intelligence operation revealing suspicious WhatsApp communications with individuals based in Pakistan.
Karnataka Home Minister Priyank Kharge confirmed the suspect was in custody as investigators probe the extent of potential indoctrination.
This incident marks the third recent arrest in the region connected to alleged social media-based conspiracies against national security.