Interview medium options:

According to UPSC Civil Services Interview (Personality Test) rules:

• You may use English, Hindi, or the same Eighth Schedule language as declared in your Mains medium for the interview
• This is declared in DAF-II (filled after Mains results)
• The interview board is constituted with language capability to match your declared medium

English vs Hindi in interview — practical data:

Based on LBSNAA analyses and coaching institute surveys:

• Approximately 90%+ of interview candidates use English, even those who wrote Mains in Hindi
• Reason: UPSC interview boards typically include senior IAS/IPS officers and domain experts who may have stronger English
• Hindi-medium interview candidates report that the conversation quality depends on the board — some boards are more comfortable with Hindi, others less so

Can you switch mid-interview?

Officially, no — you declare a medium and the board prepares accordingly. In practice, if you stumble in one language, boards may accommodate a phrase or two in another, but this is at the board's discretion and should not be relied upon.

Recommendation:

• Use the language in which you can express nuance, humour, and confidence — not just factual statements
• If you wrote Mains in English, interview in English is strongly advised
• If you wrote Mains in Hindi, practise mock interviews in Hindi with Hindi-comfortable panelists before deciding

Source: UPSC CSE Personality Test Rules; UPSC Notification 2025, upsc.gov.in