Member states of Mercosur
- Argentina (1991)
- Brazil (1991)
- Paraguay (1991)
- Uruguay (1991)
- Venezuela Associate state (2004), Protocol of Accession (2006), Full Member (2012)
- Chile(1996) 
- Bolivia (1996), Protocol of Accession (2012)
- Colombia (2004)
- Ecuador (2004)
- Peru (2003)
Guyana and Suriname signed framework agreements with Mercosur in July 2013 to become associate states. These agreements will enter into force following their ratification, which is subject to legislate approval in each state.
Venezuela applied for membership, but its entry has not been ratified by Paraguay, although it was ratified by Argentina, Brazil and Uruguay. However, in June 2012 Paraguay was suspended from Mercosur for an alleged coup d'état and the violation of the Democratic Clause of Mercosur, so Venezuela's admission, already approved by the remaining members, became effective on July 31. Venezuela is considered a key member of the Mercosur due to its energy resources, including natural gas and oil. Venezuela is also an important economic market for Brazil because of a favorable balance of trade.
Ratification process in Brazil
The process was approved by the Brazilian Government, the Chamber of Deputies and the Senate. In May 2007, the Brazilian Senate asked Venezuela to reconsider the non-renewal of RCTV's license, an oppositionist television network. Venezuelan president Hugo Chávez responded by accusing the Brazilian Congress of being subservient to interests of the United States. The leader of the Brazilian Social Democracy Party in the Senate, senator Arthur Virgílio, stated that the party will try to prevent Venezuela's entry in Mercosur. On December 18, 2008, the Brazilian Chamber of Deputies approved by 265 votes, 61 against and 6 abstentions, Venezuela's bid for membership in Mercosur. The bill was forwarded to the Brazilian Senate, where it was still pending as of 31 May 2009, though Brazilian President Luiz Inácio Lula da Silva said he expected final approval by September. However, some members of the Senate condemned Hugo Chávez's alleged attacks on freedom of the press and expression in Venezuela. One senator Flexa Ribeiro said, "The Brazilian Senate needs to send a strong message in support of the reestablishment of full democracy in Venezuela." The decision could further delay Venezuela's entry into Mercosur.
In September 2009 President Luiz Inácio Lula da Silva said that he is confident the Senate will approve the entry of Venezuela and added that "There is no Senate opposition to the entry of Venezuela into Mercosur. What exists is a natural process of discussion of the senators who want to evaluate the pros and cons of the enlargement of Mercosur with Venezuela's entry." According to Lula, the expansion of the organisation will especially benefit the northern states of Brazil. The ambassador of Brazil in Caracas, Antonio Simões was called to Brasília to meet with 81 senators and explain the benefits of Venezuela's entry into Mercosur for Brazil.
Ratification process in Paraguay
The government of Paraguay supports Venezuela's entry into Mercosur but this process is complicated by opposition from the right-wing Colorado Party. The party had ruled Paraguay for 61 years until 2008 and controls still Paraguay's Upper House whose support is needed to pass the bill. On March 4, 2009, the External Relations Commission of the Paraguayan Chamber of Senators could not approve a recommendation for Venezuela's bid for membership in Mercosur. The bill was later withdrawn by the Paraguayan government after it feared defeat in the Congress, after several legislators questioned Hugo Chávez's "commitment to democracy" following the closure of several media outlets in Venezuela. President Lugo called on Congress to avoid “prejudices” and not limit a country of millions of souls “to an only name”, after a June 2010 political agreement between the President’s coalition and the Colorado party that renewed speakers at the Senate and the Lower House.
The Paraguayan Senate's block on Venezuela's membership was circumvented in June 2012, when the country was suspended from Mercosur for an alleged coup d'état and the violation of the Democratic Clause of Mercosur, so the admission of Venezuela (already approved by the other legislatures of Mercosur) became effective on July 2012.
Future new members
Bolivia and Ecuador have expressed interest to join the bloc. However, their membership in the Andean Community of Nations complicates such attempts. Peru's president Humala said in 2011 that Peru may be interested in joining in the future, but that the country was not yet ready to start the process due to economic reasons.
Bolivia's full participation in the Mercosur bloc has been under negotiation since June 2011. In December 2012, Bolivia signed an accession protocol to become a full member. Uruguay ratified the agreement in June 2014. In September 2014 Argentina approved Bolivia's entry, leaving only Brazil and Paraguay left to approve the agreement.
Ecuador started negotiations to join Mercosur in May, 2013. 
- "Se formaliza adhesión de Venezuela al Mercosur". Ministerio de Relaciones Exteriores de la República Bolivariana de Venezuela. Retrieved November 22, 2013.
- "Os venezuelanos estão chegando". Instituto de Pesquisa Econômica Aplicada. Retrieved November 22, 2013.
- "Presidentes dos países do Mercosul se reúnem para discutir integração do bloco". Governo do Brasil. Retrieved November 23, 2013.
- About Mercosur
- Argentina National Communications Commission (CNC) offial webpage
- Venezuela officially welcomed into Mercosur trade bloc during ceremony in Brazil (31 July 2012) Reuters. Retrieved on 1 August 2012
- Mercosur official webpage
- "Guyana-Mercosur Framework Agreement". Mercosur. Retrieved November 23, 2013.
- "Suriname-Mercosur Framework Agreement". Mercosur. Retrieved November 23, 2013.
- "Quienes Somos". Mercosur. Retrieved November 23, 2013.
- "Tratados, protocolos e acordos firmados após julho de 2012". Mercosur. Retrieved November 23, 2013.
- Bragon, Ranier; Andreza Matais (2007-09-22), "Folha de São Paulo", A Chávez, governo prevê aprovação neste ano, São Paulo, São Paulo: Folha da Manhã S.A., p. A10
- Venezuela and Mercosur
- Brazil - balance of trade - Venezuela
- Bragon, Ranier; Andreza Matais (September 22, 2007), "Folha de São Paulo", Congresso brasileiro reage a fala de Chávez, São Paulo, São Paulo: Folha da Manhã S.A., p. A10
- Brazil Senate leader against Venezuela in Mercosur. Stabroek News. March 6, 2009.
- Brazilian Congress puts Venezuela inches closer to Mercosur. MercoPress. December 18, 2008. Retrieved on 22 December 2008.
- "Brazilian President is confident Venezuela joins Mercosur, Noticias Financieras, 31 May 2009.
- Brazilian Senate condemns Venezuela further delaying its Mercosur bid. MercoPress. September 4, 2009.
- BBC in Portuguese
- Paraguayan Chamber of Senators does not approve first attempt to grant Venezuela membership in Mercosur El Universal. Retrieved on 4 March 2009.
- Paraguayan government withdraws bill for Venezuela's Mercosur incorporation. MercoPress. 14 August 2009.
- Lugo calls Congress to vote for Venezuela’s Mercosur incorporation (June 28th 2010) http://en.mercopress.com Retrieved on 17 July 2010