The processes taking place during isothermal melt crystallization of poly(N-methyldodecano-12-lactam), PMDL, and subsequent heating include three consecutive steps: (i) After cooling from the melt, a primary lamellar structure melting at about 51 °C is formed. Imperfect secondary crystallites are formed during later stages. (ii) On heating, additional crystallization of the primary lamellae takes place with the optimum at about 30 °C. (iii) On further heating, the primary crystallites undergo recrystallization with optimum at about 54 °C to form final higher-ordered structure melting at 62 °C. These processes are conditioned by two conformational transitions in the PMDL molecule, viz. trans/cis on the amide bond and all-trans arrangement of CH₂ sequences. The kinetics of primary crystallization suggests heterogeneous nucleation followed by two-dimensional growth with larger involvement of homogeneous nucleation at greater supercooling. The rate constant decreases with rising crystallization temperature. Additional crystallization is a two-dimensional diffusion-controlled crystal growth process with a suppressed nucleation phase. The recrystallization mechanism involves partial melting of primary crystallites and two-dimensional rearrangement of chains into a more perfect structure. Additional crystallization and recrystallization are by several orders of magnitude faster than primary crystallization. Kinetics of non-isothermal crystallization suggests two-dimensional crystal growth and heterogeneous nucleation with partial involvement of homogeneous nucleation at later stages.