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He studied architecture at the Universidade Santa Úrsula, Rio de Janeiro. In this period he also took a course in Semiology with Professor Umberto Eco and History of Urbanism with Professor Leonardo Benévolo. In his last year of university he participated with the project “Rehabilitation of the Catete Neighborhood” of the competition organized by the International Union of Architects where he received a Medal of Honor.
In 1982, after his graduation, he traveled to New York City and took courses at Parsons School of Design. In 1983 he returned to Rio de Janeiro and married Carla Carneiro da Cunha. They have two children, Carolina and Luiza Tendler. In 1986 Tendler made his first individual painting exhibition, showing works in lacquer on wood, a technique that he developed in his atelier/furniture factory. In 1990 he moved to Recife and started to work in his atelier in Poço da Panela. During this period he made the interior design of the restaurant Mafuá do Malungo, house where the poet Manuel Bandeira was born. In 1992 he exhibited at the Museum of the State of Pernambuco.
In 1993 he was invited to show his works in Belgium. Between 1993 and 2000 he had annually exhibitions in different cultural centers in Belgium. During this period Tendler participated in the Biennial of Latin America Art in Santiago de Cuba. In 1999 he published his first book 001. with critics on his work by Raul Córdula, Edson Nery da Fonseca and Luk Vermeerbergen. In 2000 moves to Belgium. In 2001 gives a workshop in the European School with pupils of the last year of arts, resulting in a panel of 10 meters of length whose the subject is “the Man and the Environment”. Between 2002 and 2004 teaches in the cultural center De Warande in the city of Turnhout, Belgium, where he carries different workshops, such as “Chaos and Creativity”. In 2003, after an ambitious project, he publishes his second book “365 - a Visual Diary”, with introduction of the art critic Mario Helio Gomes de Lima. Between 2005 and 2007 he participates actively in the project of participative diplomacy from the ambassador in Belgium, Jeronimo Moscardo and he helped in the creation of the space Darcy Ribeiro and the gallery Marcantonio Vilaça.
- 2000 - panel about the “500 years of European culture in Brazil”. Canvas of 16 meters of length by 1,60 of height. Displayed in the National Museum of Fine Arts (Rio de Janeiro) (2000) and in the Castle Den Ouden Bareel, Vosselar, Belgium (2000).
- 2002 - “365 – a Visual Diary”."
For some time now art has been the focus of many debates which have resulted in the development of new concepts. With the advent of videos and computers, people are painting less than before. But that’s not my case. I keep on painting. Art is my way of feeling. I paint extracting mysteries. I paint not only what I see, but also what permeates my body. I like the challenge of painting images that I've never seen and I'll never see. I simply imagine an unknown route. Benign holy traumas. Wounds from kisses never given nor felt. Roads never travelled. Cities never visited. I look into my life searching for the meaning of my existence. Every day I dig up the earth, trying to find my eyes. Not those I carry, but the ones which make me see. However, the earth, capricious and inexorable, only reveals the colours which betray me with my own eyes, the eyes that make me see".  It consists of one watercolor per day and one canvas per month, in the dimensions of 1,40 x 1,40 m. throughout one year. This project was displayed in the Vromans Gallery in Amsterdam (2003) and in the Cultural Center Het Werft in Geel, Belgium (2006).
- 2003 - publication of book “365 – A Visual Diary”. Accomplishment of the project “Valencia - 117 drawings”. 2004 – Promised Land - Canvas of 6 x 1,20 meters about the Old Testament. This project was displayed in the headquarters of the periodical Le Soir in Brussels (2004) and at the Fort Napoleon as part of the Project Fort Europe in Ostende, Belgium (2007).
- 2005 - Project 6 cities. Six cities had been chosen, one in each continent. In each one of these cities the artist stayed at least ten days painting and collecting material for the accomplishment of the project. Chosen cities: Rio de Janeiro - Brazil (South America). Los Angeles - U.S.A. (North America). Brussels - Belgium (Europe). Cape Town - South Africa (Africa). Sydney - Australia (Oceania). Tokyo - Japan (Asia). The project finished in January 2007.
- 2007 - Undedun project “One who brings inside the One other”. Project in mixed media on paper. This project was displayed in the Casa do Brasil in Brussels (2007) and at the University Candido Mendes in Rio de Janeiro (2008).
- 2008 - UndeSire project “One who wants to be inside the One other ”. Project made in a book format - 80 pages with drawings in mixed media.
- 2009-2010 - soMos Project, consists of 1 panel 14,0 by 4,50 meters high, 4 panels 1,80 by 1,80 meters, 1 panel 2,40 by 1.80 meters and 10 watercolour sketches.
- 2011 - Participates at Europalia : Art in Brazil 1950 - 2011 at the Bozar Museum in Brussels / Belgium, showing his winter drawings.
- 2011 - Project Between the glance and the vision.Going beyond the concept of Open Art
- 2013 /2014 - Project 6religions
A sequel of the 6cities project was created with two more projects realized in the same process. Photos and/or videos, watercolors (4) and paintings (3) from each religion were done. This one is a research over 6 religions: Buddhism, Christianity, Islam, Hinduism, Judaism and Yoruba.
- 2014/2015 - Project 6monuments, following the 6cities and the 6religions projects, with the same approach and process, 6 monuments were chosen:
Tiananmen Square/China, Eiffel Tower/France, Taj Mahal / India, Kremlin/Russia, Teotihuacan/Mexico , The National Mall/USA were the chosen places. End of the trilogy 6cities/6religions/6monuments
- 2015 - Brazil 2015 A decisive canvas
- 2015 - Project Ronchamp
The Chapel of Notre Dame du Haut in Ronchamp had an enormous impact over Sidnei Tendler. As an Architect, since his studies he dreamed to visit this Le Corbusier’s masterpiece. After the visit he painted 2 watercolors and 2 oil on canvas.
- FRAGMENTOS. Comments about plastic arts. Raul Córdula Filho (text about Sidnei Tendler: "O Pintor se pinta") 
- Magazine Continente Multicultural. "Um pintor pernambucano na Bélgica". Mario Helio. 
- Sidnei Tendler and the post-modernity. Edson Nery da Fonseca.
- Sidnei Tendler between virtual and emotional landscapes. Olivia Ardui.
- 365 - A visual Diary by Sidnei Tendler