Chasing 213 for an outright win, the hosts were wrapped up for 159 in 84.5 overs at Keenan Stadium.
Syed Mohammad shone with the ball, picking up five for 52 runs in his 35 overs while Konwar ably supported him with figures of four for 72 in 30 overs.
Konwar completed his 10-wicket haul in the match after accounting for six Jharkhand batsmen in the first innings.
Assam, who had trounced Tripura in the season opener, earned six points from this tie.
The visitors had scored 207 all out in their second essay after Jharkhand skipper Shahbaz Nadeem (4/83) and off-spinner Sunny Gupta (3/69) knocked the stuffing out of Assam batsmen.
Resuming at their overnight score of 56 for two, Jharkhand's Rameez Nemat and Saurabh Tiwary added 53 runs for the third-wicket before left-arm spinner Syed Mohammad dismissed the opener for 42 runs. Nemat struck 4 fours and one six in his 93-ball stay at the crease.
Jharkhand batsmen failed to apply themselves on a pitch, which was assisting the spinners and kept on losing wickets at regular intervals to bundle out just before the stroke of tea.
While Syed Mohammad triggered the middle order collapse, Konwar polished off the lower order to hand Jharkhand their first defeat of the season.
Assam: 179 & 207
Jharkhand: 174 & 159 in 84.5 overs (Rameez Nemat 42, Syed Mohammad 5/52, Arlen Konwar 4/72).