Hampshire finished the first day at the Ageas Bowl in the ascendancy after recovering from 208 for six to make 286 all out and then reducing Essex to 55 for two at stumps.
The visitors lost opener Tom Westley and Ravi Bopara in the first 14 deliveries of their innings and at stumps trailed the joint LV= County Championship Division Two leaders by 231 runs.
Essex will reflect on a day of missed opportunity, having put Hampshire into bat in overcast conditions and been in the box seat at the end of the second session. But Hampshire's last four wickets, aided by a significant 41 extras, added 78 runs, to post a competitive total.
Essex faced an hour's batting at the end of the final session and were quickly two for two.
With his third delivery, South Africa Test paceman Kyle Abbott bowled Westley, offering no shot. One run and 11 balls later, Bopara gloved a catch to Michael Bates off the left-arm swing of James Tomlinson to leave Essex in trouble.
James Foster and Nick Browne, with 26 and 19 respectively, successfully navigated the remainder of the session to see Essex through to the end without further loss.
It was a day of fluctuating fortunes for Essex as they allowed a promising situation to slip from their grasp. Hampshire, meanwhile, deserved credit for a lower-order fightback which left them in the stronger position at stumps.
Essex tasted success in the second over of the Hampshire innings, skipper Jimmy Adams being caught behind off the inconsistent Reece Topley to give Foster the first of five victims.
Michael Carberry and Will Smith added 72 before the opener was caught behind for 35 off Tymal Mills, who endured an erratic bowling performance, conceding 70 runs off his 12 overs.
Hampshire, 82 for two at lunch, were forced to work hard for their runs - Jesse Ryder bowling an economical spell - and when Smith, on 34, became Topley's second victim at 107 for three, Foster's decision to put Hampshire into bat appeared vindicated.
— Karl McDermott (@Karl_McDermott) June 15, 2014
James Vince, with a neat 41, and Adam Wheater, who made a pleasing 42 against his former county which included seven boundaries, took the Hampshire total past the 200-mark.
But when Bopara made an arguably overdue appearance into the Essex attack - it took Foster until the 49th over to hand him the ball - he removed both batsmen to reduce Hampshire to 205 for five and, by tea, with Bates also gone, 208 for six.
Essex ought to have pressed home their advantage but instead, Hampshire - aided by a host of extras, which contributed the second highest score - wrested the initiative from the visitors' grasp.
Sean Ervine, Matt Coles and Abbott all made important contributions as Hampshire's lower order added 78 runs to raise the total to 286.
Bopara finished with a tidy 3-14 off his nine overs, four of which were maidens.
Essex promptly suffered two blows, but rallied to finish the day at 55 for two.
Hampshire coach Dale Benkenstein was happy with the day's work.
"We would have taken 286 at the start of the day. The first session was really tough. We could have been four down and I thought we did well to only be two down," he said.
"Two-hundred-and-fifty was a par total on that pitch. It was a tough wicket, but they gave us an opportunity to get extra runs."
Essex coach Paul Grayson added: "In the first session, we passed the outside of the bat 37 times. We could have had a few more wickets by lunchtime, but we didn't bowl well during the second session and conceded far too many extras.
"After losing those two early wickets, James Foster and Nick Browne batted well and hopefully one of them will go on to make a big score tomorrow."