We describe in Streptococcus agalactiae an atypical family of conjugative transposons named Tn GBSs which associates DDE transposition and conjugation. We present evidence that the transposition of Tn GBS2 , the prototype of this family, is catalysed by a new class of DDE transposases that are widespread in Gram‐positive bacteria. Remarkably, transposition occurs in intergenic regions, 15 or 16 bp upstream the −35 sequence of promoters, minimizing the burden on the host cell and suggesting an association between transcription and transposition. Transposition catalyses the formation of a circular intermediate that is substrate for subsequent conjugative intercellular transfer. Conjugation is initiated at an origin of transfer by a transposon‐encoded relaxase. Whereas all integrative and conjugative elements described so far encode a phage‐related integrase, Tn GBS2 is the first example of conjugative transposon whose recombination is mediated by a DDE transposase. The combination of DDE transposition with conjugation implies recombination constraints linked to the physical separation of donor and recipient molecules.