MUMBAI—Following India’s crackdown on cash, millions of residents who have never even used a credit card are leapfrogging into mobile payments, finding phone apps more accessible than plastic.

The value of mobile money transactions have more than doubled since the nullification of 86% of India’s cash in circulation in November, while those made with credit and debit cards has fallen, and check purchases have barely budged. Mobile payments still make up only a small percentage of overall transactions, but their surging popularity is being noticed.