West Ham have paid UNAM Pumas 4 million pounds for 23-year-old pacy winger Barrera, while Piquionne has moved for an undisclosed fee. Barrera, who played three times for his country at the World Cup in South Africa, has signed a four-year contract with manager Avram Grant's side.
GEAR:Get a West Ham shirt
"I am very happy to sign for West Ham United and have been really taken by the reception I have received from the players and the manager," Barrera told the club website.
"I am very fast and can use both feet. I like the one-on-one situations and to take on my opponent and beat my rivals. I like to excite the supporters."
Piquionne, 31, links up with Grant again on a three-year contract after the pair spent last season together at Portsmouth, where the Frenchman played in the FA Cup final and scored 11 goals in all competitions while on loan at the club.
"I'm very happy to sign for West Ham because my last manager was Avram," the powerful striker told the club website.
"I know Avram and I like working with him and I think he likes me. I'm coming to work hard for the squad and I hope we have a good season," the ex-St Etienne forward added.
Grant, who has already signed German midfielder Thomas Hitzlsperger, said further major additions were expected within the next 72 hours.
Follow FFT.com on Twitter
Join FFT.com on Facebook
