The Finnish ace has turned down the chance to remain at the Reebok Stadium following the Trotters' relegation last season.
The keeper has agreed a two-year deal at Upton Park, according to Sky Sports.
The Hammers are expected to confirm the deal shortly, with the 37-year-old officially joining on July 1 when the transfer window opens for the summer.
The move will see Jaaskelainen reunited with his former Bolton boss Sam Allardyce.
West Ham are looking to bolster their goalkeeping options after England keeper Robert Green turned down the chance to extend his stay with the club.
Ajax has released their away soccer jersey for the 2013/14 season. Get in the Gear.
adidas has added some color to the Predator line with this new colorway. Released on May 17. Be the first to own a pair.
Chelsea won the Europa League on Wednesday. The Blues defeated Benfica 2-1 on injury time goal from Ivanovic.
One of the top soccer cleats for control the Nike CTR360 will not let you down on the field in tight spaces.
The push for more color on their cleats, adidas has added the infrared colorway to the adiZero f50 Line.
The Liverpool 2013/14 soccer jersey is available for pre-order. The Reds are eager to compete for silver next season.
The adidas Nitrocharge is the most talked about new cleat in years. It was released on May 15 and will take your pitch by storm.
The new PUMA evoSPEED 1.2 FG. A great new soccer cleat with classic look and first time for PUMA to be on the cleat.
Bayern Munich are kings of Germany and hope to be crowned kings of Europe at Wembley later this month!
The Juventus jersey for the 2013/14 was released earlier this week. Be the first to wear the colors of the Old Lady.