Field experiments were conducted for evaluation of effects of sowing dates and plant densities on phenology and essential oil quality of cumin ($Cuminum$ $cyminum$ L.). The experiments were arranged as factorial based on randomized complete block design with sowing the dates of $26^{th}$ March, $5^{th}$, $15^{th}$ and $25^{th}$ April, and densities as 25.0, 31.3, 41.7 and 62.5 $plants.m^{-2}$. Results showed that the lowest growth period was on $25^{th}$ April. Plants sown on $26^{th}$ March had greater seed yield than those sown on later sowing dates. The earliest sowing date produced the largest seeds with a thousand seed weight of 3 g. The treatment of $26^{th}$ March ${ imes}$ 62.5 $plants.m^{-2}$ produced higher essential oil. Among tested independent variables, seed yield showed a significant effect on essential oil yield. Essential oil content improved $7.55{ imes}10^{-3}mL.m^{-2}$ per kg, increasing seed yield of cumin. Plant density did not show any considerable effect on the essential oil components of cumin. Delaying in sowing date caused a significant effect on cuminaldehyde concentration in essence; thus, a maximum value was obtained from $26^{th}$ March and $5^{th}$ April sowings. For successful seed production and higher essential oil quantity and quality, cumin must be sown until late March ($26^{th}$ March) with density of 62.5 $plants.m^{-2}$ in Tabriz region.