[RuCl(SiMe3)(CO)(PPh3)2] (1) was found to catalyze dimerization of aldehydes RC(O)H yielding esters RC(O)OCH2R (3) in a Tishchenko type reaction. Aldehydes with α-hydrogen atoms (R = Me, Et, iPr, iBu) reacted quantitatively within 2 days (5 mol% catalyst, 70 °C in C6D6) whereas those without α-hydrogen atoms (R = tBu, Ph) did not react at all. In the case of benzaldehyde (R = Ph), well shaped crystals of [RuCl(O2CPh)(CO)(PPh3)2] (4) precipitated from the reaction mixture. Molecular structures of catalyst 1 and benzoato complex 4 were established by single-crystal X-ray diffraction analyses exhibiting square pyramidal (1) and octahedral (4) complex, respectively. Using 1:1 mixture of acetaldehyde and propanal a crossed esterification reaction took place forming esters RC(O)OCH2R′ (3, R/R′ = Me/Me, Et/Et; 5, R/R′ = Me/Et, Et/Me). In the case of tBuC(O)H a crossed esterification reaction with RC(O)H (R = Me, Et) took place yielding only two products, namely the symmetrical esters RC(O)OCH2R (3, R = Me, Et) and the crossed products of the type RC(O)OCH2tBu (6, R = Me, Et). As shown with propanal, ester formation is completely suppressed by water. Because ruthenium catalyst 1 was prepared by reaction of [RuCl(H)(CO)(PPh3)3] (2) with H2CCHSiMe3, complex 2 was also used as catalyst in the reaction with aldehydes. It proved to be non-active, but in the presence of H2CCHSiMe3 (H2CCHSiMe3:RC(O)H = 1:1) catalytic formation of cyclotrimers of aldehydes (RCHO)3 (7) and aldol condensation products RCHCR′C(O)H (8, R = Et, iBu; R′ = R−CH2) was observed.