Jagielka was poised to leave Bramall Lane after a clause in his contact allowed him to following the Blades relegation from the Premier League.
However he could only leave for a minimum of £4,000,000 which the Toffees have reluctantly paid, whilst Gary Naymsith has joined for a fee of £1,000,000.
Jagielka, 26 spent ten years at Bramall Lane after coming through the youth ranks, previous he spent time on the books at Everton. With Sheffield United he helped reach the Semi-Finals of the League and FA Cup during the 2002-03 season whilst he also competed in the Play-Off Final against Wolverhampton, also in 2003.
His most successful time with United came during 2005-06 campaign when they won promotion to the Premiership as runners-up behind Reading. He made his debut as a substitute on the final day of the 1999-2000 season in a 2-2 home draw with Swindon Town.
During his time with the Blades Jagielka made 264 starts (+23 substitute appearances) and netted just 20 goals.
Naysmith joined Everton from Heart of Midlothian in October 2000 after just four years at Tynecastle, he cost the Toffees £1,750,000. He made his debut at Newcastle United as the Goodison Park club won 1-0.
The Edinburgh Defender has 36 caps and one goal to his tally as a Scotland international. He leaves Merseyside after starting 130 matches (+25) and scored seven goals.