For a first visit, choose clean, comfortable clothing suitable for a place of worship. You do not need to buy a sari, dhotī or any special outfit to attend an open class.
Some participants wear traditional Indian clothing at festivals. Head coverings and ritual dress vary by event and centre: ask the local host rather than assuming a universal rule.
Many temple prayer rooms ask visitors to leave shoes at the entrance. For cooking or maintenance volunteering, follow the relevant practical safety requirements.
There is no single universal dress code for all ISKCON visitors. Courtesy and hospitality matter more than assumptions based on gender or background.