The junior Tendulkar returned with figures of 5/98 as Delhi U-19 slumped to 394 for 9 in their first essay at the Feroz Shah Kotla Stadium at stumps on day three.
Asked to bat, Mumbai had scored 453 in their first innings with opener Divyaansh (211) scoring a double century.
Delhi still trail Mumbai by 59 runs.
Arjun's scalps included rival skipper Ayush Badoni, Vaibhav Kandpal, wicket-keeper Gulzar Singh Sandhu, Hrithik Shokeen and Prashant Kumar Bhati.
Arjun, a promising left-arm pacer, is a regular member of the Mumbai U-19 team.
He has also played two U-19 games for India against Sri Lanka, where he claimed three wickets.
In the past, Arjun has also bowled at the nets of the senior Indian team in London and at the Wankhede Stadium in Mumbai.
First Published: November 21, 2018, 8:46 PM IST