Higgins will make the switch from Sale, while fellow centre Crockett and prop Tomaszczyk join from Worcester - with the trio all signing two-year deals.
Higgins and Crockett were former team-mates at Bath and will add experience to the back division, while 25-year-old Tomaszczyk was previously part of the academy set-up at Kingston Park.
Higgins is relishing joining the Dean Richards revolution at Kingston Park.
The 30-year-old told the club's official site: "I am excited to team up with Dean Richards and the team at Newcastle next season. I am looking forward to getting a good pre-season under my belt, and helping the Falcons get back to where they should be."
Crockett, also 30, helped Worcester back into the Premiership at the first attempt in 2010/11 and he has been won over by the visions at the Falcons.
"I was very impressed with the passion and the importance of keeping top-class rugby in the region - I want to be part of the new era," said Crockett.
"With Dean Richards at the helm and with new players being brought in to add to the quality that is already in the squad, I am confident we will be a tough team to beat next season."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
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Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
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The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.