The shipments also include some parcels that were loaded in June and arrived in India last month, the data obtained from trade sources showed.
July volumes were about 85 percent higher than year ago shipments of about 415,000 bpd, the data showed.
State refiners that had cut imports from Iran in 2017-18 due to a dispute over development rights of a giant gas field, have tied up significantly higher volumes for this fiscal year that began in April, drawn to the discounts offered by Iran.
Tehran had offered almost free shipping and an extended credit period for oil sales to India, its top oil client after China.
Iran was hoping to sell more than 500,000 bpd of oil to India in 2018-19, its Oil Minister Bijan Namdar Zanganeh said in February.
State refiners accounted for about four-fifth of Iranian oil imports in July with Indian Oil Corp. along with its unit Chennai Petroleum Corp. getting about 300,000 bpd oil from Tehran, the preliminary data showed.
In April-July, the first four months of this fiscal year, India's oil imports from Iran has risen by an annual 40 percent to about 677,500 bpd, the data showed.
Purchases from Iran could slow from August as imports from Tehran are getting tougher after the United States in May pulled out of a 2015 nuclear deal and announced the renewal of sanctions against Tehran.
Some sanctions will take effect from August 6 while others, notably on the oil sector, will take effect on November 4.
To keep its shipment flowing Iran has offered insurance for oil cargo and ships to supply oil to India, its top oil client after China.
In January-July, India's oil imports from Iran rose by more than 17 percent to about 612,000 bpd, the data showed.