Lanthanum hexaaluminate is a promising competitor to establish yttria partially stabilized zirconia as a thermal barrier coating material for Ni-based superalloy due to its relative low intrinsic thermal conductivity and low sinterability at temperatures exceeding 1100°C. Sr2+ and Ti4+ were selected as two dopants to partially substitute the La3+ and Al3+ in LaMgAl11O19, respectively. The variation in thermal conductivity with Sr2+ and Ti4+ fractions was analyzed based on structure information provided by X-ray diffraction and Raman spectroscopy. The average crystal size of LaMgAl11O19 sintered at 1600°C for 10 min by spark plasma sintering is in nanoscale. The fully dense La1−xSrxMgAl11−xTixO19 solid solution showed a minimum thermal conductivity value (λ = 1.12 W/(m K)−1,T = 1273 K) at the composition of La0.5Sr0.5MgAl10.5Ti0.5O19,which possibly reduces from the enhanced phonon scattering due to mass and strain fluctuations at the Ln3+ and B3+ sites.