Neal's deal is worth $5.75 million over two years. The left winger gets $2.25 million in the first year and $3.5 million in the second year.
Niskanen's deal is worth $3 million over two years -- $1.25 million in the first and $1.75 million in the second.
Neal, who will be entering his third season with the Stars, set career highs in goals (27), assists (28) and points (55) in 78 games last year. He was second on the Stars in goals and third in points.
In his NHL career, Neal has registered 51 goals and 41 assists in 155 games.
Niskanen, 23, had 15 points (three goals, 12 assists) in 74 games last season. His -15 plus/minus rating was the lowest on the team.
The defenseman, who will be entering his fourth season with the Stars, has 76 points (16 goals, 60 assists) in 232 NHL games.
The Stars now have all their players under contract in time for training camp, which opens this weekend in Charlottetown, Prince Edward Island.