In these proceedings two preliminary results from the BESIII collaboration on polarized Λ and $\bar \Lambda$ are reported. Both results are first observations and concern the resonant and non-resonant processes ${e^ - }{e^ + } \to J/\psi \to \Lambda \bar \Lambda$ and ${e^ - }{e^ + } \to {\gamma ^\ast} \to \Lambda \bar \Lambda$ at $\sqrt s = 2.396\,{\rm{GeV}}$, respectively. For $J/\psi \to \Lambda \bar \Lambda$ the relative phase between the electric and magnetic form factors, ΔΦ, has for the first time been determined, $\Delta \Phi = 42.4{(6)_{{\rm{stat}}}}(5)_{_{{\rm{syst}}}}^^\circ$. That $\Delta \Phi \ne 0$ allows for a simultaneous measurement also of the asymmetry decay parameters $\Lambda \to p{\pi ^ - }\,({\alpha _ - })$, $\bar \Lambda \to \bar p{\pi ^ + }\,({\alpha _ + })$ and $\bar \Lambda \to \bar n{\pi ^0}\,({\bar \alpha _0})$. The measured value of ${\alpha _ - } = 0.750 \pm 0.009 \pm 0.004$ differs by 17(3)% from the PDG value. The simultaneous measurement for the asymmetry parameters allows for the most precise test of CP violation conducted for Λ decays, ACP = −0.006(12)stat(7)syst. The reaction ${e^ - }{e^ + } \to \Lambda \bar \Lambda$ at $\sqrt s = 2.396\,{\rm{GeV}}$ is the first complete measurement of the time-like electric (GE) and magnetic (GM) form factor of any baryon as also the ratio R = |(GE/(GM)| and ΔΦ have been determined: R = 0.96(14)(12) and $\Delta \Phi = 37{(12)_{{\rm{stat}}}}(6)_{{\rm{stat}}}^\circ$. The obtained cross-section and effective form factor are σ = 119.0(53)stat(51)syst pb and |G| = 0.123(3)stat(3)syst, respectively.