Lalonde received his bachelor's degree in physics from the Université de Montréal in 1976, at the age of 20.
In 1985 he received his doctorate (Doctorat d'Etat) in mathematics from the Paris-Saclay University in Orsay[1] as one of the rare candidates below 30 years of age.
From 2000 to 2002 he was a Killam Fellow, a private-public foundation in arts and sciences that enables Canadian researchers to devote most of their time to their works.
He (co)founded several institutions, namely, with Francis Clarke (mathematician), the Institut des Sciences Mathématiques (ISM) (McGill, Montréal, UQAM, Concordia, Laval, Sherbrooke universities) based at UQAM, the first unified doctoral school in the world with 250 professors, the Centre interuniversitaire de recherches en géométrie différentielle et en topologie (CIRGET), the Institut transdisciplinaire de recherches en informatique quantique (INTRIQ) with Gilles Brassard and Michael Hilke, the Unité mixte internationale (UMI), a joint venture between the CNRS (France) and the Centre de recherches mathématiques (CRM), and the journal Annales mathématiques du Québec (Springer).
In 2006 he was an Invited Speaker with talk Lagrangian submanifolds: from the local model to the cluster complex at the International Congress of Mathematicians (ICM) that meets once every four years.