The dielectric relaxation studies of Diethylamine (DEA) + water mixtures over 11 different concentrations, at different temperature and in the frequency range 0.01 ≤ ν/GHz ≤ 50 has been determined using Time Domain Reflectometry (TDR). The dielectric relaxation parameters such as static dielectric constant (ε_s), dielectric constant at high frequency (ε_∞), relaxation time (τ in ps), asymmetric relaxation distribution parameter (β) and conductivity (κ) in the mixture has been obtained. The conductivity in water rich region confirms the formation of ammonium ion and hydroxide ion in Diethylamine-water mixtures. The heterogeneous molecular interactions and association in different species of Diethylamine-water molecules has been discussed using the Kirkwood correlation factor, Excess properties, Bruggeman factor and thermodynamic parameters and it has been confirmed that dipoles are arranged in parallel direction in a aqueous solutions.